For their attempt to bounce the Liberal Democrats into an alliance with Labour was no random and inexplicable departure from normal party loyalty. It was just the latest in a long history of similar acts.
For more than 30 years there has been a tightly-knit group around Roy Jenkins that has pursued its own agenda, sought its own alliances and established its own political orthodoxies. Anyone who dissented was left behind. The resultant splits, animosities and new coalitions have shaped the centre left's response to nine governments.
For all this time the central features of the political creed of the Jenkinsites have been remarkably consistent - a mixed economy with stable borders between the public and private sectors, fiscal Keynesianism with incomes policy, a federal Europe, multilateral nuclear disarmament with detente, and a vague egalitarianism chiefly advanced through increased spending on public services.
The Jenkinsites inherited much of this creed from Roy Jenkins's mentor, Hugh Gaitskell. It was also from working with Gaitskell that they learnt about factionalism and how to win a fight. Even before Gaitskell's death, though, the Jenkinsites had begun to assert their own identity; they took particular exception to his last conference speech when he came out against membership of the Common Market. As Gaitskell sat down and the applause rang out for his defence of 'a thousand years of history' his wife Dora surveyed the glum and silent Jenkinsites and said: 'But Hugh, the wrong people are applauding.'
When Hugh Gaitskell died it was natural that the Jenkinsites would oppose Harold Wilson, whose support for Nye Bevan they could never forgive. Yet by backing the erratic and totally unsuitable George Brown they also contrived a split with the capable Jim Callaghan.
If there is one reason why Roy Jenkins failed to become Prime Minister it is the animosity that existed between him and Callaghan. In his biography of Wilson, Ben Pimlott shows that whenever his subject was vulnerable to overthrow, he was rescued by the unwillingness of Jenkins and Callaghan to support each other.
Having defied a three-line whip over Europe and resigned Labour's deputy leadership (splitting with Roy Hattersley on the way), Roy Jenkins resumed internal opposition when Wilson was returned to power in 1974. Yet his predictable failure to win Labour's leadership in 1976 and the victory of the hated Callaghan proved too much - the Jenkinsites began to give up on the Labour Party. Roy Jenkins went to Brussels and when he came back it was to lead the Jenkinsites into the Social Democratic Party (SDP).
The history of the SDP is familiar. First there was the split with Labour, then the alliance with the Liberals, then the slow but steady campaign to merge the SDP with the Liberals. Once again the Jenkinsites went into internal opposition, this time to the leadership of David Owen. Once again, their factional skills were used with some brilliance to assert their traditional agenda against Owen's new thinking. Once again the result was complete internal victory, and complete external disaster.
If he reviews this history, Paddy Ashdown should not be surprised at recent events. The Jenkinsites have split with Gaitskell, split with Callaghan, split with Tony Crosland, split with Hattersley, split with Labour and split with Owen. Why not split with Ashdown? After all, one could see the events of the last fortnight as simply a re-division of the Liberal Democrat Party into its constituent parts - rootless radical Liberals and traditional social democrats.
Generally, the activities of the Jenkinsites have been motivated by principle and steered by honourable and able people. Often - over membership of the EEC, for instance, or the fight with the far left - the factionalism of the Jenkinsites has been creative and correct. Yet, ultimately, it has been destructive. If Paddy Ashdown can understand why, he might be able to shape a proper response.
The Jenkinsite journey has been a restless search for the correct allies for their fairly conventional social democracy. Few have proved consistent enough or powerful enough. The reason for this lies not in the allies but in the creed itself - the traditional mixed economy has been a failure, neo-Keynesianism and incomes policy have been discredited, a United States of Europe would be a disaster and higher public expenditure might strangle the market economy and make life worse for the poor.
It is perhaps hardly surprising that each new ally disappoints at the ballot box, when it is clear that only a fundamentally different political approach can succeed. The Jenkinsites should be able to understand this, since one of the best explanations of their problem was provided by their own in-house theorist, Professor David Marquand, in his book The Unprincipled Society. Marquand argued that corporatism could not succeed in the UK because of the deep roots of individualism in this country. Sadly, having explained that Jenkinsite orthodoxy and 200 years of British culture were in conflict, he concluded that it was the culture that would have to change.
The Jenkinsites are unlikely to be any happier with their new ally than they have been with the ones already discarded. They perceive Tony Blair as the man to defeat the far left and return Labour to its roots. Yet this has already been done by Neil Kinnock. Blair's task, which may prove impossible, is to move Labour beyond this. In other words, if he is to succeed, Blair will have to leave the Jenkinsite approach behind.
A senior Liberal Democrat MP, Menzies Campbell, responded to the various statements from the Jenkinsites by saying that 'a period of silence from them would be appreciated'. They should all use that time to think.
The author is director of the Social Market Foundation. Between 1986 and 1990 he was a member of the SDP National Committee.