But there was President Obama on Tuesday night, pleading guilty in a succession of TV interviews to mishandling the collapsed nomination of Tom Daschle to his Cabinet. “I screwed up,” he said.

To a certain extent, Obama had little choice but to admit the obvious. Tom Daschle and Nancy Killefer had been forced to withdraw because they had not paid all their taxes. This came after Timothy F Geithner weathered scrutiny of his own tax problems before winning confirmation as Treasury Secretary. Republicans suddenly sensed vulnerability in this new President.

Obama’s advisors said his admission showed how this presidency would by stylistically different. But the episode was revealing for reasons that go deeper than mere style. It reflected concern in Obama’s top circles that the President and his aides had put at risk his carefully cultivated political image.

It was hard for Obama to be chastising Wall Street executives for living by a different set of rules when people he was appointing into Government were perceived as doing much the same thing.

“There were two words: not just ‘mistake’, but ‘responsibility’,” Rahm Emanuel, Obama’s Chief of Staff, said in an interview.

“People like the fact that he said he made a mistake,” Emanuel said. “They hadn’t heard it from anybody in office for a long time. They heard excuses and denials.”

Yet, there is a reason that prior inhabitants of the office had been loath to admit error, given the way in which such an admission can undercut the power and the mystique of the presidency, a point that Obama’s own advisers did not dispute.

And Obama may find that this is not a well that he can return to so easily. Obama has to be particularly careful not to do anything to feed any public concern that he might not be quite ready for this job, which was precisely the argument used against him in the presidential campaign.

And there is another reason previous presidents were reluctant to admit wrongdoing.

“He’s saying the buck stops with him,” said Mark McKinnon, who was a longtime advisor to Bush. “But, the bucks can start piling up pretty fast on this job if you’re going to take the heat for every miscue.”