Though everyone in the mayor's inner circle has known about his relationship with Judi Nathan for months, no one seems to understand how he's handled it. (It is, of course, another hallmark of Giuliani's administration that none of his advisers dared discuss it with him.) "We were all scratching our heads about this," says one Republican insider. "We all understood the possible ramifications, and we were dumbfounded as to why he would expose himself to this kind of risk."

In an effort to explain it, a couple of Giuliani friends point to the impact of his illness. "When you get cancer, your life comes into focus," says a confidant, "and you start to realize what's important and start to face your own mortality. You realize you've only got so many years in this life, and you want to do what you want to do. I think that's what this is about."

His illness, however, explains only the past couple of weeks. It doesn't shed any light on why the mayor thought it was perfectly all right to have Nathan along on New Year's Eve, when Rudy-in-charge was managing the millennium celebration in front of the whole world. Literally. Or why he paraded her (again, literally) in public on St. Patrick's Day.

For that matter, it doesn't even begin to explain why barely two days after a trembling Hanover accused her husband of cheating on her twice in the past five years, Giuliani would flaunt his girlfriend. On a beautiful Friday evening, as Hanover was off to California with the kids to spend Mother's Day weekend with her parents, the mayor went to dinner with Nathan. After a leisurely meal at Tony's Di Napoli on the Upper East Side, a beaming Giuliani, accompanied by a claque of reporters, strolled with Nathan back to her apartment on 94th Street, where the two said good night. Rudy the Romantic?

"I have to believe," says one former high-level member of the mayor's staff, "that he probably hasn't been listening to the people who've given him sound advice in the past. I know he's now talking to Peter Powers, but it's a little late. Looking at the strange way he's been behaving, my guess is it's Elliot Cuker who's been giving him advice."

This was a refrain repeated again and again by people close to the mayor: He shouldn't be leaning so heavily on the advice of Cuker, loyalists told me, when making life-altering decisions. "Elliot likes to think of himself as the mayor's Svengali," says one Republican insider. "He exercises enormous influence over Rudy and he wants the mayor to remain mayor. He loves sauntering into City Hall with his bow tie and cappuccino. He loves having his parking permits and heading the Film and Theater Advisory Board and the Crystal Apple awards and producing the Inner Circle show. And most of all, he loves being able to say, 'My best friend is the mayor.' 'My best friend the senator,' to him, wouldn't sound as good." (Cuker denies this, saying he has no agenda and wants only what's best for his friend. "I can afford to fly to Washington.")

Cuker's contributions notwithstanding, there is another explanation for the dramatic change in Giuliani's behavior: He's in love with Judi Nathan. That's right, nothing more complicated than that. He's a guy in love. You can see it when he talks about her, you can see it when he looks at her, and you can see it in the way he's behaved recently.

Though all the talk has been negative -- the mayor's midlife crisis -- and the language describing his situation has been laden with portentous overtones, the mayor actually looks -- when he's with Nathan -- positively liberated. He looks buoyant, like he's happy and having fun. Which is no small thing for a man who's ordinarily as testy as Giuliani.

Not only was Judi Nathan with him on New Year's and St. Patrick's Day, but he took her to the annual Inner Circle dinner in March, an event thrown by and for reporters. Now, you could say this was simply an outrageous act of Gary Hart-like brashness ("Go ahead, follow me.").

But even as arrogant as this mayor is -- and as successful as he's been in bullying the media -- he still couldn't have confidently believed he could parade his girlfriend in front of several hundred reporters and no one would report it. (As it turned out, of course, no one did.)

But taking his girlfriend everywhere is what a guy who's in love does. He's happy, he's proud, and he wants to show off. Though one insider chalks this up to the mayor's just being the mayor ("He's not the kind of guy who's gonna try and hide"), it's unlikely he'd be so bold if the romance were less important to him. Was he trying to manipulate the media into breaking the story? Possibly. It is also possible he wanted it out to force his wife's hand.

One political insider even says he believes that Nathan, who has certainly not wilted in the spotlight, pushed Giuliani to go public. This is, of course, the classic play for a woman seeing a married man, and -- in the stereotypical scenario -- what a woman in this circumstance wants is for the man to leave his wife.

In the middle of the Giuliani drama, there was a powerful image of the mayor sitting in the front of St. Patrick's cathedral at Cardinal O'Connor's funeral. There was President Clinton with Hillary; Al Gore with Tipper; George W. Bush with Laura; Governor Pataki and Libby; and, among this group, by himself, was Rudy Giuliani. Much was made of the symbolism of this haunting picture: the mayor, forever the loner, the battler, the man who seeks no counsel, needs no comfort, and is happy going it solo in a world of his own creation.

But the reality is that this impression of the mayor as an ascetic is completely wrong. All the fire, the passion, and the emotion spilling out of him in public and directed mostly at his enemies is apparently also at play in his personal life. All this time, he's never been alone at all. He's always had a woman to rely on, to trust, and to share the excitement of his work. It just happens not to have been his wife.

Knowing what we know now, we can go back and connect some of the dots, fill in some blank spaces, and answer some nagging questions about Giuliani and his mayoralty. It is even possible to gain some insight into the extraordinary relationship that dominated his first five years in office: the one with Cristyne Lategano.

At the beginning of the summer in 1995, I began to do the reporting for a piece about Lategano, then the mayor's director of communications.

It was a year and a half into Giuliani's first term, and from a public-relations point of view, things were not going well. Giuliani's relationship with the press had been anything but a honeymoon, and the young, exuberant Lategano had become the scapegoat. Only 28 and with limited political experience, she was clearly in over her head. Her role as press secretary, always an important one in a new administration, was particularly critical in the Giuliani mayoralty for two reasons.

First, he was a Republican elected by a narrow margin in what was still a predominantly Democratic city. More important, however, he was a reformer whose politically brave assaults on the deficit and the business-as-usual bureaucratic Establishment made him the first potentially transformative mayor the city had had in years. Getting the message out is crucial in this kind of activist government, because it helps drive the policy.