It seemed unthinkable just a few months ago, when Malcolm Turnbull enjoyed a commanding lead in the opinion polls.
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But with the federal government's two-party-preferred vote in the Fairfax-Ipsos poll tightening from a 56 per cent to 44 per cent lead in November to 53 to 47 in March - and Labor leading 51 to 49 in last week's Newspoll - the unthinkable might happen.
It's less than three years since the end of the 43rd Parliament - which former MP Robert Oakeshott described as "beautiful in its ugliness" - but another hung parliament could happen. Labor, still a rank outsider, might even snatch a surprise victory.
As Victorian crossbench MP Cathy McGowan puts it: "There's never been a more exciting time to be an independent."
Here's how it would work:
A uniform swing of 4 per cent [the Electoral Commission considers a seat marginal if held by less than 6 per cent) would deliver Labor 17 seats, according to election expert Malcolm Mackerras, the creator of the Mackerras pendulum.
Add to that three more seats now considered to be notionally Labor because of a redistribution of electoral boundaries in NSW, and Labor would increase its representation from 55 to 75 seats - exactly half of the 150 on offer in the lower house.
ABC election analyst Antony Green's election calculator makes an almost identical prediction under a uniform swing of 4 per cent.
An increase in Labor's two-party vote, from 46.5 per cent in the 2013 election to 50.5 per cent, would deliver 74 seats for the ALP, 71 for the Coalition, and five on the crossbench - and another hung parliament.
But swings are not uniform, and the marginal seats campaigns that each party runs will be crucial in saving, or winning, government.
Mr Mackerras said the chances of a hung parliament were as high as one in five if, as seems likely, the Senate fails to pass laws to re-establish the construction industry watchdog and a double dissolution is held on July 2.
"I'd say there is one chance in 10 of a hung parliament in an October or November House of Reps, half-Senate election, and one chance in five in a double dissolution in July," he said.
"At a double dissolution in July, Turnbull will be at more risk. It will be a worse result. I'd say Turnbull would win with a six-seat absolute majority in July, and a 12 to 14 seat majority in an October or November election."
Mr Mackerras said the "sophomore surge" – a term used to describe MPs contesting their second election gaining an increase in their personal vote, even if their party suffers a swing away from them – would probably ensure the return of the Turnbull government.
"It wouldn't actually surprise me if the swing to Labor was 5 per cent and Turnbull still won the election because of the sophomore surge," he said.
Across the country, Mr Mackerras nominated the seats of Capricornia, Banks, Eden-Monaro, Lindsay, Page, Robertson, Deakin, Gilmore, Reid and Corangamite – all held by first-term Coalition MPs – as among those likely to defy a swing back to the ALP and benefit from a sophomore surge.
Ms McGowan said she did not want to hazard a guess about whether a hung parliament would eventuate, but if it did, "I've been saying to everyone in my electorate there will be no deals".
Tasmanian independent Andrew Wilkie said: "I won't enter into any agreement with any party to help them form government."
But Greens leader Richard Di Natale said in March it was almost "unthinkable" his party could enter a coalition with the Liberal Party – indicating Labor could probably count on the vote of lower house MP Adam Bandt.
Liberal strategists contacted by Fairfax Media wouldn't countenance another hung parliament, and Labor strategists insisted their party and their leader were "in it to win it".
Or as Mr Shorten put it at a press conference on Wednesday: "I appreciate that the question recognises we're in this next election with a chance."
