His personality—in all its combativeness, confidence and excess—informs both the style and the substance of his White House bid.

Last month, confronting the question of whether water-boarding constitutes torture, the former mayor remained determinedly equivocal.

“It depends on how it’s done. It depends on the circumstances. It depends on who does it,” he said.

The comment was peculiar enough to elicit an angry rebuke from Mr. Giuliani’s Republican colleague, John McCain.

“All I can say is that it was used in the Spanish Inquisition, it was used in Pol Pot’s genocide in Cambodia and there are reports that it is being used against Buddhist monks today,” Mr. McCain said.

The other candidates, Mr. McCain added, “should know what it is. It is not a complicated procedure. It is torture.”

Mr. Giuliani’s remarks about torture also pointed up something else: that he is prone to an even more extreme version of the kind of thinking, both tactical and ideological, that characterizes the current administration.

He displays an uncommon ruthlessness about smearing opponents as soft on terror, regardless of the accuracy of his assertions or the extent to which they debase political discussion.

And he seems to have no problem signing up for the kind of double-standards on torture and human rights that have gravely undermined America’s moral authority across the globe. Is there a more succinct expression of American hypocrisy than the notion that whether or not a given action is torture “depends on who does it”?

Such positions would have little chance of gaining traction were it not for the dogged way in which Mr. Giuliani has kept himself wrapped in the garb of September 11 and national security.

It is well-known, at least in this city, that doubts about Mr. Giuliani’s character long pre-dated this campaign. The most famous examples include his offensive (and literally inaccurate) description of Patrick Dorismond, the unarmed black man shot dead by the NYPD in 2000, as not “an altar boy,” to his decision to let his second wife know he was leaving her by announcing the news at a press conference.

But even on those occasions, Mr. Giuliani’s tendency toward narcissism was not as jarring as it has become in his pronouncements on September 11.

In August, as questions about the lack of safety precautions for rescue workers in the aftermath of the tragedy finally received national prominence, Mr. Giuliani declared, “I was at Ground Zero as often, it not more, than most of the workers. I was there working with them…So in that sense, I’m one of them.”

The former mayor tried to back-pedal the following day by acknowledging that he “could have said it better.” In the process, however, he got himself into more trouble: “I was there often enough so that every health consequence people have suffered, I could also be suffering,” he said.

A New York Times examination of official records found that Mr. Giuliani was at Ground Zero for around 29 hours from September 17 to December 16 2001. (Records were not kept before September 17.) A study of over 1000 September 11 rescue and recovery workers by the Mount Sinai Medical Center found that the median time those people spent at the site was 962 hours.

Small wonder, then, that Mr. Giuliani’s comments caused such anger among first-responders. They were variously described as “disgracefully insulting” and “self-absorbed and delusionary” by representatives of firefighters’ labor unions.

But Mr. Giuliani is willing to invoke the terrorist attacks to cover up for even the most trivial misstep.

When he came under criticism for the seemingly contrived cellphone conversation with his wife that ‘interrupted’ his speech to the NRA in September, he offered this defense in an interview with the Christian Broadcasting Network: “Quite honestly, since September 11, most of the time when we get on a plane we talk to each other and just reaffirm the fact that we love each other.”

To most Americans, September 11 is a tragedy, an outrage and a scar upon the nation. Mr. Giuliani, to be fair, probably feels those things too. But for him, the distinction between the events of that period and his own political reputation has long since been elided.

He has sought to use the greatest atrocity in living memory for his own advancement.

Therein, perhaps, lies the secret of his success. But it is also the reason why Mr. Giuliani’s campaign nauseates his opponents just as much as it thrills his supporters.

*The original version of this story contained an inaccurate quote taken from an AP story that was subsequently corrected.