Scott Morrison faces losing a key ally with the South Australian Liberal government expected to fall at this weekend's state election.
A loss for SA Premier Steven Marshall would run counter to the trend which has seen every incumbent state and territory government facing COVID-era elections returned, many with thumping majorities.
It would leave the national cabinet table with just two state and territory Liberal leaders - NSW and Tasmania - to Labor's six.
The prime minister is weighing up the timing of a federal election, widely expected to be held on May 14.
While few federal seats are expected to change hands in SA, much of the focus has been on Boothby, where incumbent Liberal MP Nicolle Flint is retiring.
Ms Flint has been the subject of horrendous sexual harassment and online abuse, accusing Labor's federal leadership of failing to call out attacks by union supporters and activist groups during the 2019 election campaign.
The seat will be a fascinating battle between Liberal candidate Rachel Swift, Labor's Louise Miller-Frost and independent Jo Dyer, who like Ms Flint has championed the end of "toxic politics".
State Labor in SA has been leading not only in the two-party vote in published polls but Labor leader Peter Malinauskas has been ahead of Mr Marshall as preferred premier.
The numbers are already difficult for Mr Marshall.
In the 47-seat lower house, the government has 22 seats to Labor's 19.
There are six independents, with three elected as Liberals but splitting from the government during the term to sit on the cross bench.
When Labor lost the 2018 election it had been in power for 16 years.
The unique thing about the 2018 loss was the Labor government received a swing towards it, but new electoral boundaries did not work in its favour.
A key issue for voters in SA will be Mr Marshall's decision to reopen the state's borders in November and general handling of the COVID-19 pandemic.
While health has been a key issue for Labor, the Liberal campaign has been based around the economy and jobs in industries such as defence and space.
Mr Morrison has been eager to provide millions of dollars in support for SA's manufacturing industry, and talk up the opportunities in the defence sector.
But a Roy Morgan poll taken this month gave Anthony Albanese's federal Labor team 52.5 per cent of the two-party preferred vote in SA, up almost two points on the 2019 federal election result.
On his trips to Boothby, Mr Albanese has underlined Labor's commitment to key road projects, clean energy, lifting wages, improving child care and overcoming the skills crisis.
A closely watched factor will be the strength of the vote for independents and minor parties, which will play a key role in the SA Senate race.
Independent senator Rex Patrick and Centre Alliance's Stirling Griff are up for re-election and could see themselves out of a job if either the Greens vote picks up (it doubled in 2019) or the major party vote strengthens.
The Greens are running economist and jobs expert Barbara Pocock as the lead candidate and are hopeful of adding a number to their ranks alongside high-profile SA senator Sarah Hanson-Young.
The Liberals have tended to get a higher Senate vote in SA than Labor, outpolling the ALP by around 10 percentage points in the past three federal elections.
