Mayo by-election, 2018

Cause of by-election
Sitting Centre Alliance MP Rebekha Sharkie resign on May 11, 2018, due to her being a dual citizen at the time of nomination for the 2016 election, after the High Court clarified the constitutional requirements on May 9, 2018.

Margin CA 5.0%

Parts of South Australia to the south and east of Adelaide. Mayo covers the Adelaide Hills and the coast of South Australia from Lake Alexandrina to the southern edge of Adelaide, as well as Kangaroo Island.


Mayo was first created in 1984 as part of the expansion of the House of Representatives. The seat has always been held by the Liberal Party, although it has always been a high-profile target for minor parties.

The seat was won in 1984 by Alexander Downer, son of former cabinet minister Alec Downer and grandson of former premier Sir John Downer. He retained the seat safely in 1987 but was challenged by the Democrats in 1990, with the minor party polling over 20%. Downer retained the seat with a 6% margin.

A redistribution and a fall in the Democrats vote saw him retain the seat easily in 1993 and 1996. In 1998, the Democrats ran John Schumann, best known as lead singer of the band Redgum. Schumann achieved over 22% of the primary vote and reduced Downer’s two-party margin to 1.7%, the closest the Democrats ever came to winning a House of Representatives seat.

Another favourable redistribution in 2001 helped Downer win re-election, and he was untroubled at the 2004 and 2007 elections. Downer had served a disastrous year as Leader of the Opposition from 1994 to 1995 and served as Foreign Minister for the entirety of the Howard government from 1996 until 2007. After the defeat of the Howard government in 2007, Downer moved to the backbench and retired in 2008 to serve as United Nations envoy to Cyprus.

The ensuing by-election was contested between Liberal candidate Jamie Briggs and Greens candidate Lynton Vonow, as the ALP did not stand a candidate. The Greens polled 21%, and the Liberal vote dropped to 40%. After preferences, Briggs won 53% of the vote, and retained the seat by a slim margin.

Jamie Briggs was re-elected in 2010 and 2013.

Briggs lost Mayo in 2016 to Nick Xenophon Team candidate Rebekha Sharkie.


  • Tracy-Lee Cane (Christian Democratic Party)
  • Kelsie Harfouche (People’s Party)
  • Major Sumner (Greens)
  • Georgina Downer (Liberal)
  • Rebekha Sharkie (Centre Alliance)
  • Stephen Humble (Liberal Democrats)
  • Reg Coutts (Labor)

This is a difficult seat to predict. Sharkie should benefit from incumbency, but the circumstances of the by-election are unusual. We also don’t know what impact the departure of Nick Xenophon and the change in the party name to Centre Alliance could have on Sharkie’s support.

2016 result

Jamie Briggs Liberal 35,91537.8-16.1
Rebekha SharkieNick Xenophon Team33,15834.9+34.9
Glen Dallimore Labor 12,85913.5-7.6
Nathan Daniell Greens 7,6618.1-6.1
Bruce HicksFamily First4,3754.6-2.5
Luke DzivinskiLiberal Democrats1,1481.2+1.2

2016 two-candidate-preferred result

Rebekha SharkieNick Xenophon Team52,28355.0
Jamie Briggs Liberal 42,83345.0

2016 two-party-preferred result

Jamie Briggs Liberal 52,65055.4-7.2
Glen Dallimore Labor 42,46644.6+7.2

Booth breakdown

Booths have been divided into five areas, based on local government boundaries. three groups cover all of the polling booths in a single council area: Kangaroo Island, Mount Barker and Onkaparinga.

Polling places in the Adelaide Hills and Barossa council areas have been grouped as “Adelaide Hills”, while those in Alexandrina, Victor Harbour and Yankalilla council areas have been grouped together as ‘South’.

Over one-third of ordinary votes were cast in the Adelaide Hills, with just under a third cast in the south of the seat.

The Nick Xenophon Team won a majority of the two-candidate-preferred vote in all areas, ranging from 51.1% on Kangaroo Island to 59.6% in Mount Barker.

Labor came third, with a primary vote ranging from 10.9% in the Adelaide Hills to 16.6% in Onkaparinga.

Voter groupALP prim %NXT 2CP %Total votes% of votes
Adelaide Hills10.956.223,44324.6
Mount Barker14.259.612,17112.8
Kangaroo Island11.051.12,1262.2
Other votes15.053.018,58319.5

Election results in Mayo at the 2016 federal election
Toggle between two-candidate-preferred (NXT vs Liberal) votes and Labor primary votes.

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Ben Raue is the founder and author of the Tally Room.If you like this post, please consider donating to support the Tally Room.