After basking in the national spotlight for months as a presidential tease, Mayor Bloomberg faces the prospect of diminished political relevance after ruling out an independent run for the White House.

Coming less than two years before the end of his mayoralty, Mr. Bloomberg’s decision to stamp out once and for all speculation about his ambitions has left the political classes wondering: If he’s not a candidate for president, does he still matter?

His trips to far-flung locales such as Bali and China, and his speeches on immigration, global warming, and gun control, have attracted widespread attention, but they were linked, at nearly every turn, to the prospect that he might run for president.

Mr. Bloomberg’s best chance at ensuring his relevancy as the Democratic and Republican candidates march toward November may be as a running mate, but political observers say it is unlikely, if not impossible, that the Republican front-runner, Senator McCain, or the Democratic frontrunner, Senator Obama, would invite Mr. Bloomberg to share their ticket.

Endorsing a presidential candidate, as Mr. Bloomberg indicated he would do under the right circumstances, may do little to keep afloat his national political profile or give him a few fleeting moments on the national stage.

“There aren’t millions of people waiting on the edge of their chairs for Mike Bloomberg to endorse,” a professor of political science at the University of Virginia, Larry Sabato, said. “It’s over. He’s not going to be running for president. He is not going to be a vice presidential nominee, and he’s not even going to have a great influence on who is elected.”

The mayor shot down the idea that he might end up in the White House in the no. 2 spot, saying yesterday, “Nobody is going to ask me to run as vice president.”

He was speaking to reporters for the first time since he stated that he would not run for president in an op-ed article in the New York Times.

“I just think that the best way I can make a difference in this country is by being a mayor that makes a difference in this city,” he said yesterday. “New York City is a bellwether. It is a leader in ways that I don’t think New Yorkers understand.”

Mr. Bloomberg said he did not think his ability to disseminate his message would diminish now that he has closed the door on a presidential campaign, and said there was no reason for him to create an independent political group that could attempt to influence an election, known as a 527.

“If I want to get a message out, I think it’s relatively easy to do that. I have not been adverse to getting people together to support and get the message out,” he said.

Mr. Bloomberg wrote that he would help a candidate who challenged party orthodoxy and adopted practical solutions to problems facing the country.

The mayor’s supporters in New York City argued yesterday that Mr. Bloomberg wouldn’t fade from the national spotlight simply because he definitively decided to not run for president.

Mayor Koch said Mr. Bloomberg has the ability to focus the presidential candidates and the public on important issues, and he called the mayor an “educator in the grandest sense of the word.”

“Anybody who has billions of dollars available to him to support causes and candidates is always going to be heard and listened to,” Mr. Koch said.

A former aide to Mr. Bloomberg, William Cunningham, said an end to the presidential speculation would help Mr. Bloomberg in his campaigns to raise awareness about issues such as public health, the environment, and education.

“Now when he talks about issues that affect the city and now when he talks about initiatives that the city is undertaking, people will look at it in that context and not in the context of, ‘Oh, this must have something to do with a national run for office,'” he said. “And so that will be very helpful to him as he tries to focus more attention on some areas he really cares about.”

Indicating that Mr. Bloomberg may still garner some attention on the campaign trail, Mr. Obama indicated yesterday that he would court his support, saying he hopes Mr. Bloomberg would “conclude that I’d be in the best position to put forward the kind of pragmatic, common sense solutions that he’s championed in New York.”

“And I will definitely be reaching out to him,” he said.