Given how much Nick Clegg has staked on the Lib Dems remaining in government after the next election, and Labour's stubborn poll lead, it is unsurprising to find him warming to the prospect of a coalition with Ed Miliband's party. He tells a Radio 4 documentary to be broadcast tonight: "I think they've [Labour] changed. I think there's nothing like the prospect of reality in an election to get politicians to think again and the Labour Party, which is a party unused to sharing power with others is realising that it might have to."
By contrast, he says of the Tories: "I think the Conservative Party has changed quite dramatically since we entered into coalition with them. They've become much more ideological, they've returned much more to a lot of their familiar theme tunes. I think it would be best for everybody if the Conservative Party were to rediscover a talent for actually talking to mainstream voters about mainstream concerns."
It seems Ed Balls's recent overtures in the New Statesman have not gone to waste.
Clegg does, however, qualify his remarks by warning that "if there were a Labour-Liberal Democrat coalition, we the Liberal Democrats would absolutely insist that government would not break the bank."
The Deputy PM's choice of words ("break the bank") will likely perpetuate the false belief that the last government "bankrupted" Britain, but more significant is what they imply about the future. In his recent speech to the Fabian Society, Balls committed a Labour government to balancing the current budget and to reducing the national debt as a share of GDP by the end of the next parliament. While he left open the option of borrowing to invest, his chosen fiscal rules make large public spending cuts unavoidable.
For Clegg, however, this may not be enough. In his speech on the economy at Mansion House last week, he backed George Osborne's more aggressive post-2015 deficit reduction plan and vowed to pursue it if the Lib Dems were in government after the next election. "In the autumn statement we set out a plan to get debt falling as a proportion of GDP by 2016-17 and to get the current structural deficit in balance a year later. That is the right timescale and the one to which the Liberal Democrats remain absolutely committed. If I am in government again, this is the plan I want us to stick to."
Osborne's plan differs from Balls's in three important respects: it is based on a commitment to reduce the national debt by 2016-17 (rather than by the end of the parliament), and to achieve an absolute budget surplus by 2020 (rather than merely a current surplus), and, therefore, would not allow the government to borrow to invest in infrastructure.
But while Clegg has made it clear that he favours Osborne's timetable, others in his party, most notably Vince Cable, are fighting for an alternative approach. In his own recent address on the economy, the Business Secretary said: "There are different ways of finishing the job … not all require the pace and scale of cuts set out by the chancellor. And they could allow public spending to stabilise or grow in the next parliament, whilst still getting the debt burden down." Based on that, it seems that Cable would prefer to adopt the approach taken by Balls, leaving room to borrow to invest depending on the state of the economy, rather than Osborne's ideological fixation with a budget surplus.
The key question, in the event of another hung parliament, will be how far Clegg is prepared to go to bind Labour to a plan that he deems fiscally responsible. Given the emphasis he has put on the issue ("we the Liberal Democrats would absolutely insist that government would not break the bank"), it's possible that he would veto any agreeement that did not include Osborne-style cuts.
Alternatively, given Labour's superior bargaining power, it's possible, or even likely, that Miliband and Balls would get their way. In a reverse of 2010, when he signed up to early spending cuts, despite having consistently opposed them throughout the election campaign ("merrily slashing now is an act of economic masochism," he warned, adding that "If anyone had to rely on our support, and we were involved in government, of course we would say no."), he could move from backing Conservative cuts to backing a more balanced plan.
Whatever happens, now Clegg has named his terms, the debate over post-2015 cuts will move up a gear.