James Purnell's surprise announcement that he will be leaving parliament at the election is a big blow to Labour. First, the party has lost one of its brightest and most innovative thinkers. Purnell is one of the few MPs who has genuinely sought to rethink the relationship between the state and the market in the wake of the economic crisis, and his recent essay for the Guardian provided one of the most thoughtful and articulate discussions of the limits of the Third Way.
Second, the media will present his resignation as another vote of no confidence in Gordon Brown's leadership. Earlier this week, Purnell told LabourList that he believed Gordon Brown could still win the election, but his decision to stand down suggests that he didn't fancy the long, hard slog of opposition.
Purnell's critics have already suggested that the timing of his announcement, the day before Brown unveils Labour's main election themes, was designed to inflict maximum damage on the Prime Minister.
But what seems more likely is that Purnell concluded that his growing intellectual curiosity was incompatible with his status as a Labour MP -- that, as Kant once put it: "The possession of power unavoidably spoils the free use of reason."
His plans beyond his current post at Demos are unclear, but it is likely that Labour's loss will be the think-tank world's gain.