The opposition is now finding it harder to avoid the difficult questions and is beginning to outline a fiscal strategy. Most of its commitments for new spending, we are told, will now be subordinated to the overriding goal of maintaining a ''pathway back to surplus'' and of safeguarding the federal government's triple-A rating. Some promises remain cast-iron, (including abolition of the carbon and mining taxes) but many others are being made conditional on the future budgetary position. They will only be implemented when (and if) the budget bottom line allows them to be. We can expect the provisional nature of the Coalition's spending policies to become more explicit as the election approaches and public questioning becomes more intense.

Some critics will see this fudging of future commitments as a cynical cop-out, as a device for making promises which can then be safely broken. However, the tactic becomes less deceitful if public discussion emphasises the proviso that commitments depend on funding which, in turn, depends on the budget position. Voters will want to distinguish between firm, practicable commitments and more wishful promises that have little chance of being funded. Promises that appear likely to disappear over the horizon because of their cost will begin to lose their electoral appeal. Abbott's cherished parental-leave scheme is a case in point, tied as it is to a cut in company tax that is set to be postponed.

That election promises should be kept and not broken is one of the strongest values in our political culture. It is linked to the corresponding concept of democratic mandate, which licenses an elected government to enact policies that have been publicly aired during an election campaign. Whereas a mandate permits enactment of commitments, and tries to persuade others to aid their passage, promises go further and actually oblige the government to do what it says it will do.

Mandates and promises are key conventions in systems of adversarial single-party government where one party has a majority and can be held to its commitments. In multi-party systems where minority or coalition government is the norm, they hold much less sway, operating more as opening gambits in inter-party negotiations. That Prime Minister Julia Gillard was pilloried for breaking her promise on the carbon tax in order to negotiate support for her minority government reveals Australians' deep-seated attachment to single-party majority government. Hopes for a new parliamentary paradigm based on consensus and negotiation have been proved naive and illusory.

Abbott's campaign to delegitimise the current ALP government has been grounded in Gillard's broken promise over the carbon tax. He will also remember how John Howard damaged his reputation for honesty through his celebrated attempt to distinguish between ''core'' and ''non-core'' promises. Government supporters may forgive the abandoning of an election commitment if it means achieving a policy result they agree with. But critics and political opponents will seize on a broken promise as evidence that the government cannot be trusted on any issue at all. Video clips of the fated words will be filed away to be used to good effect in attack ads during the next election campaign.

Politicians therefore take particular care not to break a specific commitment. This caution often leads them into convoluted qualifications, as they seek to leave themselves sufficient wriggle-room for future action without leaving any tell-tale sound-bites that could come back to haunt them. Abbott is starting to move more into this more expansive and nuanced mode, as shown by his recent willingness to be interviewed on the ABC's 7.30. But having built his own political position on the wickedness of breaking promises, he knows he cannot afford to give his enemies any hint of such distrustfulness himself.

Few enjoy the sight of politicians endlessly ducking and weaving to avoid making a commitment they might end up breaking. But such prevarication, though distasteful, reflects a welcome unwillingness to abuse our trust. For supporters of democracy, it is certainly preferable to a style of political discourse in which politicians openly make explicit promises they fully intend to break.

Direct electoral dishonesty of this type certainly finds support in some quarters. Many in business circles, for instance, have little sympathy for electoral politics, seeing election campaigns as times when governments are induced to support bad policies in order to win votes. After the election, it is hoped, governments will have the courage to turn their back on unwise election commitments and institute unpopular policies in the long-term interests of the country. Some economists have also distrusted democracy. Milton Friedman, the doyen of neo-liberal economics, chose colonial Hong Kong as his exemplar of an effective market society and praised the regime of the Chilean dictator, Augusto Pinochet, for its economic reforms. From this perspective, broken promises are preferable to bad policies.

We can expect such voices to seek the ears of ministers in any newly elected Coalition government. They will point to New Zealand, where the National (conservative) government introduced a significant change in the tax system (an increase in the rate of GST from 12.5 to 15 per cent) without first taking it to an election. They will urge the establishment of some device, such as a post-election commission of audit, to declare that ''all bets are off'' and that the government's election commitments should be abandoned in the national interest. After all, Howard and his treasurer, Peter Costello, successfully adopted this tactic in 1996. Some state Coalition governments have also followed suit, notably in Queensland, where Costello himself is running such an audit for the Premier, Campbell Newman.

However, the prospects of repeating the 1996 experience at the federal level are now remote. Howard and Costello were able to justify their unheralded attacks on public spending on supposed surprise at a ''black hole'' in the government finances left by the previous Labor government. They could reasonably claim that their electoral commitments had depended on Labor's up-beat representation of the fiscal outlook, which turned out to be false.

In 2013, however, no federal opposition party can readily claim such insouciance about the nation's financial position. Over the intervening 1½ decades, a raft of reforms has greatly improved the transparency of government finances. Treasury regularly updates detailed fiscal projections for the current year and into the medium term. The Charter of Budget Honesty, championed by Costello, established the principle that oppositions could have their policies officially costed. The new Parliamentary Budget Office will further extend the economic forecasting support directly available to the opposition.

With such levels of economic information and expert support to help them, no opposition can now pretend to be ignorant about the likely fiscal climate in which it will seek to implement its policies. By the same token, no incumbent government can now hope to mask the seriousness of the nation's finances by offering an overly optimistic and generous budget in the run-up to an election. As many commentators have pointed out, the coming budget is likely to be the current ALP government's toughest budget so far, overturning the conventional wisdom about pre-election budgets. Increased fiscal realism before an election is another factor militating against claims of fiscal surprises after the election.

Ironically, the previous Coalition government helped to bring about the changed fiscal and political environment that now undercuts any convincing justification for its favoured type of radical budgetary adjustment. Greater transparency means fewer black holes. An incoming Coalition government can still be expected to make major changes to government policies and priorities, some of them kept under wraps before the election. But it will have no excuse for any post-election claims that all bets are off.

In the meantime, Abbott can expect maximum pressure from the government, the media and the various stakeholder groups, urging him to clarify the party's commitments. In choosing his words carefully, he will know that he cannot afford to offer a single promise that he cannot keep.

Richard Mulgan is an emeritus professor with the Crawford School of Public Policy at the Australian National University.

richard.mulgan@anu.edu.au