As at least 33 days must elapse between the issue of a writ and the date of a by-election, the earliest Saturday that the by-election could take place was on 16 December.
Candidates
Events
Following the win by Barnaby Joyce in a similarly Section 44 triggered by-election in the Division of New England on 2 December 2017, the Liberal-National coalition maintained its one-seat majority in the Australian House of Representatives. However, a loss in Bennelong would have left the government reliant on crossbench support. Given this unusual opportunity for an Opposition to destabilise the government's position in parliament outside of a general election, the Labor Party chose former New South Wales Premier Kristina Keneally as a high-profile candidate. In the months prior to the by-election, the 2017 Australian Marriage Law Postal Survey was conducted asking the question, "Should the law be changed to allow same-sex couples to marry?". Bennelong was among 12 of 47 federal electoral divisions in New South Wales and among 17 of 150 seats nationally to record a majority No response; with Yes on 49.8 percent and No on 50.2 percent, compared to the New South Wales result of Yes on 57.8 percent and No on 42.2 percent, and the national result of Yes on 61.6 percent and No on 38.4 percent. Parliament passed legislation to legalise same-sex marriage on 8 December 2017. On 12 December 2017, Labor Senator Sam Dastyari announced his intention to resign from the Australian Senate, after weeks of controversy over his links and interactions with Chinese donors. Commentary deriving from Dastyari's statement was mixed, with some commentators signalling it might damage the Labor brand with voters right before they headed to the polls while others pointed to the large Chinese-Australian community in the electorate who might have got an impression that the government was pushing a "China-phobic narrative", given the pressure placed on Dastyari to resign in the weeks prior. On 14 December 2017, it was revealed that Liberal candidate John Alexander had failed the requirement to declare rental income to the parliamentary register of members' interests from his $1440-a-day 100-acre $4.8-million property in the New South Wales Southern Highlands which he had purchased in June 2017.
Results
Previous incumbent and Liberal candidate John Alexander won the by-election despite a 4.8 percentage point two-party swing to Labor candidate Kristina Keneally which made the seat marginal.
The Liberal primary vote was the lowest on record in, including the 2007 Bennelong outcome which was the only election in which the Liberals failed to win Bennelong.
