HAMILTON, N.J. — As Senator McCain’s “Straight Talk Express” rumbled toward Manhattan along the New Jersey Turnpike yesterday afternoon, the last topic the presidential candidate seemed eager to discuss was the city’s biggest political mystery: Mayor Bloomberg.

Two of Mr. Bloomberg’s closest allies have endorsed Mr. McCain, and his predecessor at City Hall, Mayor Giuliani, was seated awkwardly a couple feet away, squeezed shoulder-to-shoulder into the back of the campaign bus with a handful of reporters.

If the Bloomberg boomlet is deflating, Mr. McCain showed no interest in adding any air to it.

“All I know about Mayor Bloomberg’s political ambitions is what I read” in New York’s newspapers, Mr. McCain said.

It was less than two months ago that Mr. McCain went out of his way to praise Mr. Bloomberg during an Iowa debate, saying the mayor had done “remarkable things” in reforming the city’s education system.

Yesterday, the praise was gone, and his words were clipped.

Would the newly crowned Republican front-runner actively seek Mr. Bloomberg’s endorsement? “I want the support of anyone who’ll support me,” he said.

What about the vice presidency? “The one thing we haven’t done is talk about that,” Mr. McCain said. “That kind of speculation is premature and would violate, as I say, all my superstitious tendencies.”

With comfortable leads in delegate-rich states such as New York, New Jersey, and Connecticut, Mr. McCain heads into today’s elections — which have been likened to a national primary — as a heavy favorite over his nearest rival for the Republican nomination, Mitt Romney.

Although clearly confident, Mr. McCain returned repeatedly to his “superstitious tendencies” as he chatted with reporters yesterday. He refused to discuss his strategy for defeating either Senator Clinton or Senator Obama in the fall, knocking the wooden table in front of him when a reporter dared ask about the general election.

“We’re just not taking anything for granted. You’ve got a guy out there who’s willing to spend $50 million, $60 million of his own money,” Mr. McCain said, referring to the sum that his campaign believes that Mr. Romney has contributed to his bid.

He also said he did not think voters would be turned off by Mr. Romney’s personal investment. “It doesn’t ever seem to affect voters if people spend their own money,” Mr. McCain said, although he again demurred when asked if that would apply to a potential independent candidate such as Mr. Bloomberg, who would likely spend 10 times as much as Mr. Romney to finance his bid.

Mr. McCain’s only potential obstacle to the Republican nomination appears to be an unrelenting opposition from some conservatives who are wary of his positions on immigration, the environment, and campaign finance. Rush Limbaugh has been railing against Mr. McCain on his popular radio show, and Mr. Romney has enlisted a former Pennsylvania senator, Rick Santorum, to record phone messages to voters criticizing the Arizona senator.

Mr. Romney’s campaign yesterday also tried to link Mr. McCain to the 2004 Democratic nominee, Senator Kerry, by sending an e-mail to reporters with a series of old news articles reporting that Mr. McCain made an unsuccessful push to be Mr. Kerry’s running mate.

Trying to hold the conservative flank, the McCain campaign last night launched a national ad hitting Mr. Romney for changing his position on key issues over his career. The spot, titled “Trust,” shows a widely circulated video clip of Mr. Romney distancing himself from the legacy of President Reagan. “Mitt Romney was against Ronald Reagan before he was for him,” an announcer intones. “If we can’t trust Mitt Romney on Ronald Reagan, how can we trust him to lead America?”

As Mr. McCain’s campaign raced to run a last-minute ad before Super Tuesday, the candidate himself did his part on the bus. Portraying the former Massachusetts governor as a panderer who is out-of-step with fiscal conservatives, Mr. McCain cited his support for ethanol subsidies in Iowa and billions of dollars in government aid to the auto industry in Michigan. He also held aloft a copy of yesterday’s Boston Globe, which reported that the cost of the health care plan Mr. Romney signed in Massachusetts had doubled.

“I don’t think Romney is going to succeed in getting to the right of me,” he said.

Mr. Giuliani sat quietly for much of the bus-ride discussion yesterday, jumping in when prompted by Mr. McCain or when responding to the occasional question from a reporter. The one-time Republican front-runner has become a popular opening act for Mr. McCain, and arrived to enthusiastic cheers at a firehouse rally yesterday in Hamilton, N.J. He joked to the crowd that after getting trounced by Mr. McCain in the early primary states, he finally beat him on Sunday night, winning a friendly Super Bowl bet. “At least I won something from him: the Giants,” Mr. Giuliani said to laughter.

He played the same role a couple hours later at a rally at Grand Central Terminal, where Governor Pataki threw his support to Mr. McCain. The brief and modest rally in Vanderbilt Hall served as a reunion of sorts for city Republicans and in particular for Messrs. Giuliani and Pataki, whose relationship was occasionally rocky. Missing, of course, was the one-time Republican who may yet have a say in the presidential race: Mr. Bloomberg.