-- John McCain is trying to escape Madison Square Garden to get to a birthday brunch in his honor. He turned 68 Sunday. He will be 72 on Election Day 2008, if anyone's keeping track.

Anyway, McCain's on his best behavior today. He is doing his best imitation of an on-message, on-the-reservation, smartly saluting Republican. Of course, part of the enduring appeal of McCain -- particularly among his fans in the media -- is that he is not always on his best behavior and not always on-message.

But this is a week for the maverick Republican to warm himself in the campfire glow of the GOP reservation. When McCain declares, "I'm here to rally the troops for President Bush," or says Bush is a leader of "great clarity," his words become increasingly effusive, just as his criticisms of the president are more muted.

Asked about the bitter primary campaign against George W. Bush in 2000 -- as he has been relentlessly this weekend -- McCain declares that he "will not look back in anger." That it would be "inappropriate" to do so, and that "looking back in anger is counterproductive" to what he wants to accomplish. Also counterproductive would be any perception that he doesn't support the president and that he secretly -- or not -- is rooting for his Senate friend, John Kerry.

McCain is trailed, as always, by clusters of reporters and their nostalgia for a man less hinged. Appearing on CBS's "Face the Nation" Sunday from the floor of Madison Square Garden, he says again that he'll "not look back in anger" at 2000.

Afterward, a reporter asks him, begs him, to look back in anger at 2000. Just for a few minutes, for old times' sake.

"Sorry, can't help you, my boy," McCain says, laughing. "Not today."

And not Monday night, when McCain addresses the convention. And not Tuesday, when McCain spends the day campaigning with Bush, and not Friday, when he campaigns with Bush again.

"I am being asked by the president of the United States to campaign with him more than any other American is," McCain is saying in an interview Saturday night in his plush suite at the Lowell Hotel. He has been watching an interview with the historian Niall Ferguson on C-SPAN. Graphics come on the screen listing Ferguson's favorite books, and McCain is volunteering which of these books he himself has read ("I've read Bismarck, I've read Disraeli . . . read 'War and Peace,' of course, read 'Moby Dick' ").

McCain speaks of how he enjoys his campaigning with Bush. To ride around on Air Force One is a labor of honor, he says, if not necessarily love.

"Now, I like the president," he says. "I really do. I will look you right in the eye and tell you that I really like the president of the United States. He really is pleasant."

And McCain really is a Republican!

"Sometimes people forget that," he says. He can be prone to helping people forget that by breaking with the Bush administration on a roster of key domestic issues (tax cuts, stem cell research, global warming and gay marriage, among others). Or by saying -- as he did earlier this year -- that he would "entertain" the idea of being Kerry's running mate.

But there has been a marked shift in the warmth with which McCain has discussed Bush in recent weeks -- and, more subtly, in how he talks about Kerry. While much has been made of their friendship, McCain, according to sources close to him, has grown weary of Kerry's constant mentions of it. He publicly objected to Kerry's reference in a recent ad to Bush's campaign tactics against McCain in 2000. (Kerry promptly pulled the ad.)

Asked if Kerry has overstated the closeness of their bond, McCain says, "Yes and no."

"Yes, in that we've spent a lot of time working on issues, flying to Vietnam, doing a lot of that kind of professional Senate work," McCain says. "No, in that I've never socialized with him. I've never been to his house for dinner. We've never invited him out to Arizona."

Cindy McCain, who is sitting next to her husband on the couch in their suite, shakes her head. "I bet we've had 20 senators out to Arizona," she says.

"I've been to John's house in Georgetown once," John McCain says of Kerry, "like six or seven years ago. And I've never been invited up to Nantucket. Or Sun City. I mean Sun Valley [Idaho]. Or whatever."

McCain says he feels he has no fences to mend at the convention this week. But he is proceeding like a man shopping for goodwill in the GOP, a realm where his loyalty is, at best, suspect. A subtext to McCain's intra-party goodwill tour is that he may run for president again in 2008. It's a prospect he denies -- if not definitively -- but one that has been discussed within his circle and among party insiders.

If McCain does run, his most adoring constituencies -- independents and the media -- can only get him so far. He needs hard-core Republicans, the kind who vote in primaries, and who, by many accounts, are noticing his recent support of Bush.

"He has clearly gone a long way to winning the hearts and minds of the faithful," says Ed Rogers, a Republican lobbyist. "Clearly the buzz here [in New York] is that, hey, isn't it great that we've got McCain? Isn't it great that he's making such an effort."

Implicit in this is that McCain is a self-contained force, someone to be crossed at peril. A July CBS poll showed that Bush had lost significant support among independents. Bush and Kerry were virtually even among independents in polls taken in the spring, but Kerry opened up a lead of 17 points in the July poll. Indeed, one of the amusing byproducts of McCain's stature is getting to watch Bush and Kerry tread so lightly around him.

Last Thursday, Bush called McCain to say that he wanted to work with him on legislation that would limit the influence of 527s, groups named after a section of the tax code that spend large sums of money to buy and produce political ads while still officially unaligned with the presidential campaigns. It is a 527 that's behind the recent ads that accuse Kerry of inflating his record as a Navy Swift boat commander in the Vietnam War -- an ad that McCain has criticized and asked Bush to condemn. Bush's phone call to McCain -- and McCain praising Bush for his commitment to curtailing 527s -- won widespread notice.

The next day, Kerry called McCain, which received no notice.

"It was sort of a casual, how-are-things-going kind of thing," McCain says. Kerry reiterated in the conversation that he was angry about the Swift boat ads. "He didn't tell me anything he hadn't said publicly," McCain says, adding that he's not exactly sure why Kerry called.

McCain chuckles at the situation. It's not often that someone gets called by both presidential candidates within 24 hours. "When you think about it, it's just strange, this whole thing," McCain says. "I make one statement and the phones are ringing off the hook and Democrats are saying, 'That McCain, he'll do anything that Bush wants.' And then I'll say this other thing and the Republicans will say, 'That McCain, he's a traitor.' " He laughs. "I tell you, it's just strange. I get flooded either way. It's like walking on a razor blade for me."

He loves walking on razor blades, clearly. He is rushing out Madison Square Garden, after a speech rehearsal, crossing paths with Rudy Giuliani, laughing as he heads off to his birthday brunch at the "21" Club.

No, he says in response to a reporter's question, he has not heard from Bush today. Or Kerry. "But it's still early," McCain says. Not even noon. "Nothing from Nader, either."

As he leaves the floor, McCain is met by NBC's Tim Russert. Russert, grinning, is holding up a small whiteboard sign that says "McCain in 2008?"

McCain grabs a marker and scrawls a response. His answer, which is hard to read, starts with an "N," has a "Y" in the middle and ends with "T."

It says either "Nyet" or "Not Yet."

The Arizona senator with his wife, Cindy, at Madison Square Garden.Sen. John McCain, center, tours the convention site with wife Cindy and Henry Kissinger.