London is taking over Paris as the favorite city of the French. The French presidential candidate, Nicolas Sarkozy, flew in last week for an election rally. The 300,000 citoyens who have fled here from an overtaxed France makes London the sixth largest French city. The French grumble that the British are exporting their old people, who retire to la France profonde, while they export their young people to the British capital.

But London has taken over something else from France — surrealism. There is no other word to describe the atmosphere in Westminster just now, as each day brings new speculation about Scotland Yard’s investigation of Downing Street. The thought of detectives interrogating a prime minister while in office, and arresting members of his inner circle, about a crime that may never have happened and which nobody really understands, would not have occurred to Sherlock Holmes even in one of his cocaine-induced hallucinations.

Just because it has never happened before, however, does not mean that it isn’t happening now. Tony Blair and his entourage are under investigation on suspicion of offering honors in return for donations to the Labor Party. They are also being investigated for possible obstruction of justice.

As with Watergate, the original crime is less serious than the cover-up. There has always been a degree of ambiguity about the exercise of prime ministerial patronage. Tories would say that Mr. Blair has been notably more blatant than previous prime ministers in his distribution of peerages, but the truth is probably rather that public tolerance of an inherently corrupt system has worn thin. Just because nobody has been sent to jail for selling honors since the mid-1920s does not mean that it can’t happen now.

Few people can understand the fine line that separates the legal from the illegal rewarding of political donations. Everyone, however, can understand obstruction of justice. Those who want Mr. Blair to leave Downing Street in handcuffs do so on the basis that he could have ordered his staff to delete crucial e-mails or other incriminating evidence during the police inquiry.

Mr. Blair for his part seems confident, even to the point of insouciance, that not only he but also his close aides will be exonerated. He may well be right.

Yet the consensus is that the mere fact of the scandal is doing immense damage to his party, his government, and — most seriously of all — to his office. Fears of damaging the prime minister’s office will not save Mr. Blair, rather, they may hasten his political demise.

As usual, the consensus is at least partly wrong. The office of the prime minister has existed in its modern form for three centuries, and it will take more than a minor scandal to do any serious damage. Ironically, Mr. Blair has done more to limit his own power of patronage — a prerogative that ultimately derives from the Crown — than any of his predecessors.

The only reason a few controversial cases have aroused the attention of the press, and then of the police is because the distribution of honors is now far less shrouded in mystery and far more carefully scrutinized than ever before. If Mr. Blair had been content to carry on as usual without reforming a system that he rightly saw was opaque and undemocratic, he would not now be in trouble.

My own view is that it will take more than a whiff of scandal to drive Mr. Blair out of office. Indeed, an early resignation would be tantamount to an admission of guilt. He does not look like a man who thinks the game is up.

The real tragedy is that the British people, unlike the man they elected three times to lead them, have lost sight of the mission. The defense of Western civilization is a mission that Mr. Blair does not want to leave half accomplished, but it looks as if he will have to do so — he has promised to step down no later than this fall.

The Conservatives are relishing this prospect, as they well might be. Even with all his troubles, though, Mr. Blair’s party is only three points behind in the polls. Many Conservatives were privately dismayed when their foreign affairs spokesman, William Hague, last week claimed that Britain was “uncritically aligned” with America and should instead realign itself with the emerging superpowers, China and India. The public, too, suspects that the Tories are not yet ready to return to office.

Why, despite the daily ordeal that he endures, does Mr. Blair remain in office? There is a one-word answer to that: Iran. I suspect that he and President Bush know more than the rest of us about just how imminent the crisis is. And the thought that Mr. Blair might still be around when it happens is a reassuring one.