He could have stopped it with a click of his fingers. The former home secretary Charles Clarke will not be alone in reflecting bitterly that had Gordon Brown supported Tony Blair at the beginning of last week the Labour party could have avoided days of disastrous infighting.

The chancellor has performed incompetently. For years he has held back from staging a coup because he knew that Labour would be ungovernable afterwards. But now, without striking openly against his leader, he has shown himself to be untrustworthy. He remained silent too long, he was grudging in his belated statement of support on Thursday, and when he left a meeting with a beleaguered Blair, he was caught grinning more broadly than we had ever seen before.

Clarke has done more than merely add to the barrel of bile spewed from the Labour party last week. He has created a lasting image of Brown as slippery and unreliable. The chancellor is pigeonholed. Having stayed his assassin’s hand to the point of appearing irresolute, Brown has branded himself a traitor, almost as if he had wielded the dagger.

When Margaret Thatcher was brought down in 1990, the Conservative party had one other superstar: Michael Heseltine. But he was the principal culprit in her demise, and that was enough to deny him the leadership. Even those who had wanted her gone balked at rewarding the lead plotter.

When John Major unexpectedly resigned as party leader in 1995 and invited challengers, I did not offer myself for election, mainly because it would have been impossible to command the support of a new cabinet if I had busted apart the old one. Brown will find it difficult to lead a united government. Senior ministers know how much damage Brown’s surliness has done to Blair and to the government’s programme.

Once lost, party discipline is difficult to restore. Having deposed Thatcher, the Tory party has made each of her successors live on a knife edge. The Labour party will be the same. Disappointed Blairites will owe no allegiance to Brown. Some of them will relish his difficulties and the opportunity to humiliate him in retaliation for Blair’s treatment.

Labour backbenchers are now aware of what power they wield. Conventional wisdom had it that Labour did not depose its leaders in office. The textbooks must now be rewritten. Even the most successful and powerful premier in Labour’s history must take dictation from those deemed unworthy to hold salaried office, not so much the great unwashed as the great unpaid. That is bad news for Brown.

The rise of dissent against Blair can be mapped against two events: Labour’s decline in the opinion polls and the alignment of the government’s foreign policy with America’s.

The Labour party is massively too sensitive to the polls. Blair’s achievement of keeping the government ahead of the opposition for nine years is unparalleled. Thatcher consistently trailed Labour but moved ahead at election time. Labour MPs went soft during all those years that Blair led in the polls. Now pathetically they are in turmoil because they are somewhat behind the Tories, with three years or more remaining before an election.

If Brown is judged by the same criteria, he will not last long. It is the norm for the opposition to be ahead, but as Thatcher demonstrated, that does not foretell the next election result. It is likely that David Cameron will continue in front. After all, Labour appears to have a death wish and is now more interested in its own issues than the electorate’s.

The polls suggest that Cameron’s lead will grow when Brown takes over. The chancellor may enjoy a bounce in support on entering 10 Downing Street, as Major did, but he should no longer count on it.

Major was a breath of fresh air, because he was almost unknown. Brown is grimly familiar to us all. Major had a winsome smile. The chancellor’s resembles a fault line in Scottish granite.

Labour finally lost its patience with Blair over his support for Israel in Lebanon. Following the catastrophe of the Iraq war, it was the last straw. The pressure is on Brown to divorce himself from the United States. He has kept (disgracefully) silent on Iraq and Lebanon, so his options are open. But it would be amazing if he began his premiership by pulling out of Iraq (and/or Afghanistan), causing a breach with Washington. He could not easily put an honourable gloss on a British retreat.

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