I make the argument in a commentary in this week's New Statesman, illustrated by an all-smiling triumvirate of Gordon Brown, Nick Clegg and Vince Cable.
Despite a growing sense of Conservative triumphalism, It may well be very difficult for either major party to win a clear majority at the next General Election. The Conservatives will clearly outperform how they did in 2005 under Michael Howard. But they remain very much untested as a government in waiting; and require a very large and possibly double-digt lead on election day to win any majority at all. Labour's electoral coalition was badly fractured in its weak 2005 result, and the economic crisis makes incumbency more difficult, even if the government can make a strong case that it has the better response.
A hung Parliament must be a real possibility. But I set out why I don't think that would lead to either a Tory-LibDem or Labour-LibDem coalition, but rather a David Cameron minority Tory administration.
However, my argument is that there may still be one chance to address the 'progressive dilemma' of the 20th century so brilliantly articulated by David Marquand back in the early 1990s. It depends on forming a Labour-Liberal Democrat coalition now, to govern for a year ahead of a General Election. It sounds unlikely: but I set out the terms of a deal which I think would be worth doing on both sides.
Labour supporters will believe the party can still bounce back and win. I agree. Labour are the underdogs but nothing is certain in politics.
Were such a coalition possible, I also think it would be a better government. It could reinvigorate the centre-left, test the Tories properly, provide a broader basis for a politics of fairness to respond to the recession, and make possible the deeper reform of British politics through a new constitutional settlement which has always eluded centre-left governments over the last century.
Many may say that Labour would not offer such a deal, or that the LibDems would not accept it if they did.
But what if they could?