Tony Abbott has accomplished something that Bill Shorten could not. He has made Shorten Australia's preferred prime minister.

Today's Fairfax-Nielsen poll shows that 51 per cent of voters would prefer the Labor leader to be prime minister, over 40 per cent who favour Abbott.

And the Opposition Leader has pulled ahead earlier than in any prime minister's term in 40 years.

The poll shows that the budget was a landmark moment in political unpopularity.

''There have only been less popular prime ministers on a handful of occasions'' in the 40-year history of the survey, pollster John Stirton said.

Those include when the Whitlam government was embroiled in the notorious Khemlani loans affair, when Paul Keating broke his ''L-A-W'' promise to deliver tax cuts, and when Julia Gillard announced the carbon tax.

Abbott was already a uniquely unpopular new prime minister in the early months of his term. But that was based largely on voters' fears and suspicions.

His first budget has confirmed the fears and validated the suspicions. The poll shows that the strongest objections to the budget are twofold: that people expect it will make them worse off personally, and that it is unfair.

Abbott and his Treasurer, Joe Hockey, could have worn the first as a badge of pride. They had promised a tough budget to fix the nation's deficit.

But unfair? That was never an Abbott promise. Or, as Stirton puts it: ''The election was Abbott's mandate to fix the budget. It was not a mandate to fix it unfairly.''

The hostile reaction to the budget has done Labor's work for it. Labor is suddenly ahead on primary votes for the first time in four years.

As UMR Research pollster Stephen Mills observes: ''Labor, at one stroke, has had its traditional positioning of representing the interests of the low- and middle-income families, looking after pensioners, defending Medicare, caring more about education and jobs and looking after the vulnerable spectacularly reinforced. The Liberals have vacated the field.'' However, the electorate is readier to acknowledge that the budget does move Australia towards a balanced budget. Asked whether the budget was economically responsible, respondents were closely divided, with 49 per cent answering yes and 48 no.

But the sharp overall movement against the Coalition was decisive and well beyond the poll's 2.6 per cent margin of error.

''The politics of the Australian budget,'' Mills says, ''seem so bad that you can only conclude that Abbott and Hockey must genuinely believe they are doing the right thing and will receive the electoral rewards of a booming economy in 2016.'' And it is that timing which explains why Abbott and Hockey are not panicking. Governments have hit these lows before and recovered to be re-elected. This poll puts the government behind by 56 per cent to 44 on the election- deciding measure, the two-party preferred vote.

The Howard government hit this low point in 1998, 2001 and 2004 yet recovered to win. As Stirton remarks: ''Recovery is always an option, especially when it's this early in the term.''

This is Abbott's and Hockey's first budget, not their third.

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