Last week's joint statement was an innocuous-seeming document, bathed in the Blairite reasonableness of "working together where parties agree", and yet no one can doubt that it is a significant step towards coalition. The paradox is that a formal coalition would be a good thing: it would have to be open, negotiated, clear about its terms. Instead we have the hugger-mugger of spin and speculation around an ambiguous relationship between two party leaders.
Above and between Mr Blair and Mr Ashdown smirks the Cheshire Cat, Roy Jenkins, the old man in a hurry behind it all, Mr Blair's guarantor of intellectual and historical respectability and Mr Ashdown's biggest asset, wheeled into last Wednesday's fractious meeting of Lib Dem MPs to help win the vote.
But the imprimatur of Lord Jenkins cannot conceal the real motives of the principals. Mr Blair would like to absorb the Lib Dems into a coalition called New Labour, an ambition candidly expressed by Philip Gould, the Prime Minister's pollster, in his book tellingly entitled The Unfinished Revolution. While Mr Ashdown, another impatient man, cannot really want to lead his party into a third election and is looking for a proper job where he gets to make decisions which are not immediately voted down by a polytechnic of obstreperous local councillors.
In any case, the intellectual basis of the Jenkins reading of history should be challenged: he argues that Labour and Lib Dems should work together because the division between the liberal and socialist traditions handed over the government of Britain in the 20th century to the Conservatives. But the real reasons for Tory dominance in the 1930s and 1980s were because the Labour Party itself split. And in the 1950s the Tories managed to win three elections in a row when hardly anybody voted Liberal. As an intellectual tradition in Britain, socialism may have lacked self-confidence - but Mr Blair has sensibly replaced it with something else, and whatever the something else is, it is not really liberalism.
Isaiah Berlin's biographer has revealed that Mr Blair wrote to the philosopher last year, shortly before his death, asking for his help in "appropriating the great aspects of the liberal tradition". But Berlin thought, with some justification, that Blair did not like the core idea of liberating the citizen from the oppressive state.
All the more need, then, for the Lib Dems to preserve their identity as the liberal conscience of the nation. That does not mean that they should refuse to work with Labour. But the basis of co-operation should be that Labour won only 43 per cent of the vote last year, and that, in return for their support, the Lib Dems should have real influence in a libertarian direction. Mr Ashdown argues that his gamble is worth the prospect of electoral reform, but that is still a distant and uncertain possibility.
A proper coalition would make it easier for the Lib Dems to retain their distinctive identity. And it would not mean that the parties should cease to contest elections - indeed, it is essential that they should continue to do so. The Lib Dem executive should reject the joint statement today, and require Mr Blair to offer the party something tangible in return for its support in future.