I used to rejoice when Tories defected to Labour. Now it makes my heart sink. The defection of Robert Jackson, the Tory MP for Wantage, represents the old Blairite one-card trick, which we also saw in 1995 (when Alan Howarth defected) and 1999 (Shaun Woodward). Just when the Conservatives are ready to launch their spending plans, they are rocked back on their heels. Instead of challenging new Labour's right to govern, the Tories are left trying to justify their right to exist.
The Blairites win elections by destroying the space for the Tories, and what better symbol of that success than a new convert? In Blair's own words, "like many people who used to be Conservatives, he [Jackson] now finds new Labour closer to one-nation politics". In other words, Blair has repositioned Labour as the party of classic one-nation conservatism. And it works, as shown by the latest opinion poll, with its projection of a 160-seat Labour election victory. The surprise is not that Jackson has defected, but that more Tories haven't jumped ship as the Blairite tide rises around them.
But this is no zero-sum game as new Labour wins one and the Tories lose one. Jackson was an education minister under Margaret Thatcher. Like all the Tory converts, he was there during the attacks on trade unions and local government, during the poll tax and the huge increases in inequality justified by the bogus "trickle-down" theory. Only now has Jackson had enough. But he is still as keen on the market as he was under Thatcher. That is why he voted with the new Labour government for tuition fees, the high water mark of marketisation - at least so far.
The debate within Labour is now about whether the rich need to pay higher taxes if the government is to meet its anti-poverty targets. Will Jackson vote for increased taxes to redistribute to the people he helped make so poor in the first place? Is he all of a sudden a progressive? Will he help shift the centre of British politics firmly to the left? I doubt it. I would suggest that Jackson's switch signifies something rather less than a conversion to equality, liberty and solidarity. People have every right to change their minds - but is it Jackson's mind that has changed, or Labour's?
The Blair strategy of denying the space for alternatives to the left or the right works for two reasons. First, because the Tories let it: they won't say what they know in their hearts - that Blair is doing many of the things that come naturally to them, such as being as tough as possible on crime and commercialising the NHS.
Second, Labour allows it. As long as we have power, we think, what is the problem? In the wake of the latest revelations about Blair-Brown rows, Labour MPs gave the two men a good telling-off for fighting in public. At last they found their voices, but only when they thought their seats were under threat. Where were Clive Soley and Claire Ward - and the others who reportedly spoke out - when it really mattered? Why didn't they give Blair a dressing-down over Iraq or tuition fees?
To many on the left, "four more years" is beginning to sound more like a prison sentence than an opportunity to renew British politics, empower citizens and close the gap between rich and poor. Jackson's conversion will help seal what Jackson wants - another big majority that enables the government to be "unremittingly new Labour", precisely because the party will be defending seats, people and places which are anti-progressive and so will never allow the redistribution of wealth or the democratisation of politics. Instead of refashioning Britain in the image of the left, Labour will be refashioned by the likes of Robert Jackson. Margaret Thatcher said "there is no alternative". There won't be unless the democratic left decides it wants one.
Neal Lawson is managing editor of the Labour journal Renewal (www.renewal.org.uk)