Tonight, as Prime Minister Kevin Rudd listens to his Treasurer, Wayne Swan, present the Budget that will lead the Government into this year's election, a political sword will be slicing the air above his head.

Rudd, who after winning power in 2007 enjoyed one of the longest honeymoons with voters anyone can recall, is now in deepening trouble.

Two new polls have confirmed the findings of last week's Newspoll, with all three warning that Rudd is in danger of becoming the first Prime Minister in more than half a century to be dumped after a single term.

In the past few days his Deputy Prime Minister, Julia Gillard, has been forced to deny speculation that there are moves to eject Rudd and install her as leader.

"[Rudd] is leading the Government in what have been some difficult circumstances, leading the Government as we front up to some hard decisions, leading the Government as we provide the economic leadership that people want and need," she said.

Rudd's most important bid to win back voters, a new 40 per cent "super tax" on miners to redistribute wealth and fund new social and nation-building programmes, has rebounded on the Government in the latest polls.

It has also drawn the bitter and heavily-funded opposition of the mining industry, resentment in the crucial Liberal-governed mining state of Western Australia, and the promise of Opposition Leader Tony Abbott to block the legislation in the Senate - or to dump it if he wins power.

Rudd has been floundering since it became clear that the bulk of his key first-term promises from the last election will not be met, most importantly the shelving of his greenhouse emissions trading scheme.

The ETS was the Government's central climate change policy and the issue on which Rudd staked his claim to moral and economic leadership. It has now joined a lengthening list of failures, backflips and disasters, and a series of interest rate rises that is expected to continue.

Rudd is now refocusing on health and social policy, repositioning himself as national care-bringer and suburban champion, areas that will be featured in an otherwise austere budget to be sold as responsible economic policy to cement future prosperity.

There will be funding for a national programme to rejuvenate public hospitals and primary healthcare, including taxpayer-funded nurses for the nation's GPs, cheaper prescription drugs, skills training, and a new round of personal tax cuts already scheduled.

Swan will also announce extra funding to cope with the rising numbers of asylum seekers arriving by boat from Indonesia, a dilemma given tragic new force by the apparent loss of five lives in the Indian Ocean. The Government has already been hurt by its response to the resurgence of boat people, including the suspension of visas for asylum seekers from Sir Lanka and Afghanistan and the decision to re-open the Curtin detention centre in remote northern WA.

A Nielsen poll in Fairfax newspapers yesterday gave Rudd a dark warning that Newspoll's finding last week that the Opposition now led Labor might in fact have reflected a more substantial shift among voters. Labor now trailed the Opposition in primary votes and was 50-50 in the two-party preferred vote that decides Australian elections.

The Sydney Morning Herald said this represented a 2.7 per cent swing against Labor which, if uniform, would be sufficient for Abbott to win power.

The Morgan poll confirmed that the Opposition led the primary vote and was neck-and-neck in the two-party vote, with more voters disapproving than approving of Rudd's performance.

"For the first time, the Rudd Government is no longer a certainty to be re-elected," pollster Gary Morgan said.

Abbott told ABC radio the "field evidence" showed voters saw Rudd as the leader of a government that broke promises, wasted money and which did not know how to undertake reform. "I think there is a developing crisis of confidence about Kevin Rudd's capacity to govern effectively."

The Government dismissed the poll as the product of a few bad weeks. "There's always going to be periods in the life of a government when you go through a bit of a difficult patch and I think we've just had one," Finance Minister Lindsay Tanner told the ABC.