Political impact of expanding territorial Senate numbers


As a follow-up to Thursday’s blog post, I wanted to look into the question of what would actually happen if the territories were granted a third or fourth Senate seat.

It’s easy enough to calculate the primary vote quotas in past elections. It’s relatively easy to make guesses about who would have won those extra seats (although not without room for debate), and thus to calculate the net impact on the left-right balance in the Senate.

It is clear that for most of the history of territorial Senate representation, the addition of extra seats would either have no impact or favour the left by net two seats.

Then finally I try to tackle a more complex question: does this expanded Senate do a better or worse job of reflecting how people vote?

This entire article assumes that the territories would continue to elect their entire Senate delegation at once every three years.

Let’s start by looking at voting patterns in the two territories. First up, ACT.

On this chart, I’ve drawn lines to indicate the new quotas. If the territory elects four senators, the quota would be 20% (solid line). If the territory elects three senators, the quota would be 25% (dashed line).

As with all of Australia, we’ve seen the major party vote decline. Until 2022, this didn’t make any difference to the seat results, but the vote trend was happening regardless.

Until 2010, Labor was steadily over two 20% quotas. The Coalition was generally below that number but relatively close to it.

The Greens primary vote from 2004 to 2019 was always at least 16%, which would be enough to win a seat if the territory elected four. In 2022, the Greens vote dropped substantially with David Pocock’s candidacy. Presumably if there were already four seats there would be an incumbent Greens senator and it’s unlikely that Pocock would have run.

If there were just three seats in the ACT, it is clear that the broad “left” would usually win two of them. In recent years that second left seat would usually have gone to the Greens, until Pocock in 2022. Prior to 2004, it would have usually been a second Labor seat although the Democrats would have won it twice.

Then let’s look at the primary votes in the NT:

The two major parties have always been in a position to clearly win one seat each in a three-seat election, and until the mid-2000s both major parties were usually in a position to clear 40% each.

Since 2010, the Labor primary vote dropped below 40%, but usually with more than the Greens. The CLP primary vote has dropped since 2016, as the vote for other parties has increased.

By my estimate, the four seats would always split 2-2 between Labor and the CLP, and even if the major party vote drops it’s likely the NT would continue to elect two each from the left and the right, unless there was a substantial swing in one way or the other.

On the other hand, if the NT elected three senators, that third seat would be more marginal and could flip back and forth between left and right, although generally that seat is more likely to go to the left – usually Labor, but the Greens may have won it at high points.

Next up, these charts show my estimates of who would have won each race in 3-seat and 4-seat scenarios.

Of course there’s a bit of guesswork here. I’ve started by awarding seats on full quotas, and usually then giving the final seats to the leading candidates, but I do look at what other preferences are available – if there’s a lot of Greens preferences, that might push Labor into the win over a slightly higher-polling Liberal.

In the 3-seat scenario, there is no option of an even split between left and right, which has tended to be the typical result in territory and state Senate elections over the last 30 years.

For the ACT, the left has won 2 out of 3 at every election since 1977. In early years Labor would have won two. In more recent years it was the Greens and then David Pocock.

For the NT, the left would have won 2 out of 3 at every election since 1987, except for the 2013 election.

Having four seats does create the option of a 2-2 tie, and it does happen, but the ACT is generally too progressive for that outcome at a majority of elections.

The NT has split 2-2 at every election since 1975 – Labor winning two at every election, and the CLP winning two at every election except 1987, when a separate Nationals party would have won the second right-wing seat.

For the ACT, the Liberal Party would have managed to win two seats at seven out of 18 elections, but not once since 2007. The Democrats would have won a seat off the Liberals on a number of occasions between 1984 and 2001, and the Greens from 2007 until 2022, when the seat would have gone to Pocock instead.

It’s worth noting that a 3-1 split in the ACT would be consistent with the result in 2022, when the left won two out of two seats. So whether a 3-1 split would be considered to be advantageous to the left partly depends on what you expect would happen in the future under the status quo 2-seat scenario. I suspect that the left would find it easier to win a 3-1 split than it currently is to win a 2-0 split, but both will be quite possible to achieve.

So for the next chart, I have compared my expected results to the actual results in both scenarios, to determine how much the left was advantaged at each election.

The only election where the right would have been favoured was in a 3-seat scenario in 1975, when the Coalition would have gained both extra seats.

Out of the 14 elections from 1983 until 2019, the 3-seat scenario would have advantaged the left at eleven elections, and the 4-seat scenario at ten elections.

Neither scenario would have shifted the left-right balance in 2022. This is because the actual result was 3 left and 1 right senators, and the alternative scenarios would have been 4-2 or 5-3.

So you can’t argue with the assertion that the left would benefit from an expanded territorial Senate representation. Perhaps not at every election, but over time it would often help the left and never help the right.

The next question I had is: would this make Senate elections fairer, or less fair? Generally the default result in Senate elections is an even split between the left and right 3-3. The ACT would be different, since it leans quite strongly to the left. The 4-seat scenario would largely neutralise any left bias in the NT, but would increase the impact of the left’s advantage in the ACT, since they would be winning 3-1 rather than 2-1.

Firstly, I decided to calculate the Gallagher index of disproportionality on the actual Senate results since 1990, and on the alternative results in 3-seat or 4-seat scenarios. This is a calculation of proportionality of the overall national result, comparing seat results and vote results per party. I’ve also included the House index as a comparison. Bear in mind that a higher score indicates a less proportional result.

Overall the index doesn’t shift much, and it isn’t consistently more or less proportional in any scenario.

The 3-seat scenario performs noticeably better in 1993, 1996 and 2004, when Labor would have gained two extra seats (or one Labor and one Greens in 2004).

All of the scenarios have been less proportional in the last decade, but the scenarios are all very similar in recent years. In 2022, the 3-seat scenario would have been more proportional than the actual 2-seat result or the 4-seat scenario.

The final chart in this long blog post compares the proportion of the vote and the proportion of the seats for each of the five main blocs who have won Senate seats over the last three decades.

Now we know that there is also a substantial vote for a wide variety of other parties which have often had no luck in winning seats in part due to the relatively low magnitude in each state, so you’d generally expect these parties to all overperform on average.

Overall it looks like the Coalition has steadily overperformed more, while Labor has generally overperformed by a smaller amount, and actually won less seats than their share of the vote in 1990, 1993, 1996 and (barely) 2013.

The Greens used to be under-represented, but since 2010 (when they started winning a seat in every state) they have usually been slightly over-represented. Generally the Greens can win Senate seats with less than a quota, giving them 1/6th of all state senators with less than 1/6th of the vote.

The first iteration of One Nation was severely under-represented in 1998 and 2001. Since their return they’ve usually been slightly under-represented, except at the 2016 double dissolution when they over-performed.

Labor and the Greens collectively outperformed Coalition and One Nation in 2016, 2019 and 2022, perhaps indicating a new trend.

Overall the evidence is unconvincing in either direction. An expansion in territory Senate numbers would often produce a boost for the left relative to the status quo, but there is not clear evidence that this would make Senate election results less proportional to how people actually vote.

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  1. Though I love the thought of the “broad left” having a perpetual 2:1 majority in the ACT senators, perhaps it would be a bit unfair while the States elect 6 at a time, almost (but not quite!) guaranteeing a 3:3 split. But if the States were increased to 14 senators each (7 at each election) then giving the ACT 3 would make perfect sense. Don’t think the population of the NT deserves any more than 2, though.

  2. If the Territory increases the number of senators – would they all have to be reelected at each election or would it move to a model similar to the states where half the allocation of senators are up for election.

    Eg Senators have 6 year terms with 2 up for election at each election.

  3. I don’t know how many times I need to answer this question even though it is obvious from the analysis above. The whole thing is based on an assumption that all territory senators are elected at the same time. If you still elected 2 at a time but for 6-year terms then absolutely nothing would change in terms of who would win, there would just be two separate cohorts. And you can’t elect 3 per territory if you split them into two cohorts.

  4. Hi Ben, it appears that Labor are actually contemplating 6 senators per territory. I don’t know if that’s 3 senators for 6 year terms or 6 senators for 3 year terms. (They’re also considering whether territories should count alongside states in referenda.)

    Source: https://www.theguardian.com/australia-news/2023/aug/06/labor-national-conference-northern-territory-nt-act-senators-referendums-territorians

    So how would having 5 or 6 senators per territory have performed in the past, and how proportionally representative would that be?

    I suspect that your preference for an odd number of senators per state would also apply to territories? So perhaps either 3 or 5 territory senators rather than 4 or 6? And like Jack suggests, 14 senators per state.

  5. with 6 senators per territory I get the following:

    ACT: 2 Labor, 2 Pocock, 1 Liberal, 1 Greens
    NT: 2 Labor, 2 Liberal, 1 Greens, 1 LDP

    ACT: 3 Labor, 2 Liberal, 1 Greens
    NT: 3 Liberal, 2 Labor, 1 Greens (but this is incredibly close and would depend on factors more nuanced than my rough estimation – 3 Liberal/3 Labor or 3 Labor/2 Liberal/1 Greens seem like they’re also very real possibilities)

    2016 seems pretty similar to 2019 except maybe Rise Up Australia would have had a chance in the NT?

  6. As i have noted, Antony Green said that any attempt to enlarge territory seats and Senators would run into trouble with the Constitution as it would dilute State representation. So – as in 1975 with Whitlam’s original law, the High Court will be involved as several states will go to it.

    As for changing the formula from “4 of 6 states” to “4 of 6 states or territories” – that requires a referendum and that would not pass in today’s world.

    Ditto with nobs on for amending section 44 to allow dual citizens to stand. Particularly if Mehreen does her usual antics that are not half as sophisticated or clever as she seems to think that they are.

  7. Paul, of course it would have to change from “of 6 states or territories” to “of 8 states or territories”. The tricky bit would be changing from a majority of 4 out of 6 states to a majority of 5 out of 8. That would potentially make it easier to pass a referendum – you could lose NSW, QLD and WA and just have to rely on having a majority of voters.
    The election of Senators can be modified without referencing the Constitution – in fact that was on the agenda for the JSCEM Inquiry into the 2022 Election. The Senate Ballot Paper Study 2016 on Exhaustion goes into this fairly deeply, especially on the distribution of excess senate votes once a quota has been reached.

  8. https://www.tallyroom.com.au/53382#comment-791375

    Odd numbers of Senators can be split into cohorts, section 13 of the Constitution says “…the Senate shall divide the senators chosen for each State into two classes, as nearly equal in number as practicable…”, i.e. round one class up and the class other down, leading to 1 senator (per state with uneven numbers) differences in class size. It would have worked fine pre-1949 with the plurality/majority systems used. Under PR it would have been similar to the pre-Casual Vacancies Referendum system half-Senate elections where vacancies varied between elections, although without the manipulability (except by post-DD division of Senators).

    The 1998 NT statehood proposal had 3 Senators, it was for territory style 3-year terms but that could easily have been challenged in the High Court and may have resulted in a 2-1 split, since section 13 says “each state”, while provisions that specifically apply only to original states say “original state”.

  9. “On this chart, I’ve drawn lines to indicate the new quotas. If the territory elects four senators, the quota would be 20% (solid line). If the territory elects three senators, the quota would be 33.3% (dashed line).”

    It looks like you’ve put the lines in the right place (25%), but the description is slightly wrong.

  10. Mark, Antony Green noted a few years ago that any move to expand territory senators would be challenged in the High Court by multiple states – as indeed the original 1975 law was.

  11. I am inclined to think ALP would try to keep all territory Senators being elected every 3 years. ALP hates “unrepresentative swill” delaying their agenda. They prefer 100% of power 50% of time to 50% of power 100% of time. This was why Whitlam had so many referendums whilst in office.

  12. In the case of four Senate seats per territory, I suspect the Greens would channel more resources and attention to gain that fourth seat instead of a major party. It would also encourage independents and possibly a regionalist party – something like Territory Alliance or Kim for Canberra. Similarly, the major parties would compete for the second seat, rather than expecting the status quo. In NT, this would be ALP-2, CLP-1, GRN-1 at recent elections.

    A three-seat race would be boring and predictable in the long-run, unless there’s a strong independent like Pocock running. There’s also the malapportionment of having three senators when Tasmania has 12. Four is not the perfect fix but it’s better than three.

  13. @Votante I’m not sure if Territory Alliance still exists. It was only active at the 2020 Northern Territory general election, where its leader (CLP-turned-independent-turned-TA founder and former Chief Minister) Terry Mills (MLA for Blain) and Labor-turned-TA MLA Jeff Collins (MLA for Fong Lim) both lost their seats to Labor. Robyn Lambley, the MLA for Araluen and formerly a CLP member (before becoming an independent and joining TA), was the party’s sole MLA after the election and even then she came quite close to losing Araluen to the CLP (the CLP finished first on primaries but Lambley managed to get 50.5% TPP, making Araluen one of the most marginal seats in the Territory). She has since left the party and went back to sitting as an independent. TA is not registered federally either and did not contest the Territory Senate or either of the two Territory seats (Lingiari and Solomon) at the 2022 federal election. TA was expected to perform better in 2020 (with ABC even predicting that Katherine would be a CLP vs TA contest, when in reality the CLP regained the seat facing Labor in the TPP contest, but was aided by the strong TA vote and the fact that TA preferences territory-wide mostly went to the CLP) but only won one seat and by a small margin.

  14. Also, @Votante, what makes you think Labor would win two Territory Senate seats? Here is the result of the Senate election in the NT:

    Labor: 1 seat (±0), 32.97% (–4.50%)
    CLP: 1 seat (±0 or +1 if you count defections), 31.70% (–4.97%)
    Greens: 0 seats (±0), 12.26% (+2.02%)
    Liberal Democrats: 0 seats (±0 or –1 if you count defections), 9.27% (+9.27%)
    Legalise Cannabis: 0 seats (±0), 2.40% (+2.40%)
    GAP (Great Australian Party): 0 seats (±0), 4.41% (+4.41%)
    Sustainable Australia: 0 seats (±0), 1.66% (+1.66%)
    Citizens: 0 seats (±0), 0.92% (+0.48%)
    Ungrouped UAP: 0 seats (±0), 0.57% (–0.66%)
    Quota: 34,540

    Given the unusually high Liberal Democrats vote in the Territory with their preferences mostly flowing to the CLP and the Greens preferences obviously mostly flowing to Labor, both Labor and the CLP would probably have two seats. The ACT Greens would win one of the four ACT seats, so if the territories get more Senators then the NT Greens could possibly be the only state or territory branch of the Greens without any representation anywhere except on the local level (i.e one or two councillors elected to the Darwin City Council and that’s it).

  15. Oh sorry I realised that my first sentence is wrong. I meant to say “What makes you think the CLP won’t win two seats?”.

  16. On Andrew Conway’s site, NT 2022 as a four-seat election narrowly elects a Green in place of ALP #2.

    And yes re post above by Babulama, NT 2016 as a six-seat election elects Rise Up Australia.

    I would be interested to see what the grounds would be for a High Court challenge to expansion to, say, 4 Senators per territory. The objections to 2 Senators were based on the idea that territory Senators weren’t allowed at all. If a government tried to impose, say, 30 Senators per territory the High Court would obviously step in and say this is an unreasonable stack but the question is where would they draw that line.

  17. https://www.tallyroom.com.au/53382#comment-791909
    One potential argument is, the more territory senators added, the more deviation there is from the nexus with the House of Reps and thus joint sittings are interfered with. However, that could have the result of the territory senators and MPs being ordered into the nexus (reversing the previous precedent on the matter).

    The first standout number for the High Court to set as the maximum number of territory senators is the same number of senators as an original state.

  18. Yes the previous precedent on the nexus (in McKellar’s case, 1977) was based on the old idea that the Territories are some sort of exceptional “add-on” in the Constitution. The High Court has walked away from that more recently (eg in Vunilagi’s case just 11 days ago) so “ordering the territories into the nexus” is quite possibly on the cards.

    And yes, giving a Territory more senators than each original state could be a bit of a red rag to the HC bull!

  19. @Jack Aranda – you also have to note that Western Australia is not in the preamble to the Constitution.

  20. If they increase the territories they will need to increase the states and that in turn will increase the size of the house

  21. The odds of a small, populist or right-wing party e.g. LDP, Rise Up, scoring a seat is quite slim in a 4-seat scenario. ALP and CLP only need 20% to gain a seat. Generally ALP and CLP get mid 30s at least. The odds of each major party reaching the second quota is quite high. Also, unlike the eastern states, there isn’t a plethora of minor parties whose elimination in the count would distribute preferences to allied parties (e.g. IMOP, ONP to UAP). Ralph Babet (UAP) scored the final Victorian seat with a 4% primary.

    The Greens can get 10% but will find it tricky to win a seat given the absence of left-wing micro parties and Labor getting just under a second quota on primaries and not 2.5 quotas.

    @Nether Portal, Ben’s bar chart above shows a 2-2 split in NT. Generally, Labor gets a higher primary vote at both the HoR and Senate levels, though they took a beating in 2022. In a 4-seat scenario, 20% is needed to get a seat, and before 2022, Labor would get close to 40%.

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