Riding a first-quarter fund-raising wave that came within close reach of Senator Clinton’s surge, Senator Obama swept through New York City last night to attend three overlapping fund-raisers and appear on “Late Show with David Letterman.”

Mr. Obama emerged from a black sport-utility vehicle with a wide smile on his face shortly after 6 p.m. yesterday to attend the first reception, at the Upper West Side home of Kenneth Lerer, co-founder of a political Web log, the Huffington Post. Mr. Lerer cohosted the fund-raiser with a former AOL Time Warner chief operating officer, Robert Pittman.

The $2,300-a-head event drew dozens of supporters, many of whom arrived outside the El Dorado building on Central Park West in chauffeured cars. Several celebrities stood out in the crowd, including sportscaster Ahmad Rashad, film director Ron Howard, and former television news anchor Tom Brokaw, who said on his way in: “I’m here as a freebie.”

Mr. Howard, who slipped in a side door, also attended a fund-raiser for Mrs. Clinton in New York City last month. At the time, he told The New York Sun he thought there were a number of exciting candidates in the presidential race, but said he had not yet decided whom to support.

A professor of public administration at Columbia University, Steven Cohen, said that by coming to New York to raise money, Mr. Obama appears to be mounting an aggressive campaign against Ms. Clinton. The city is considered the senator’s turf.

“It looks kind of like you are coming right at her,” he said, referring to Mr. Obama.

The senator raked in more than $25 million from more than 100,000 donors in the first quarter, putting him just shy of the $26 million Mrs. Clinton raised from about 50,000 donors during the same period.

Mr. Cohen said it was assumed that Mrs. Clinton would raise a lot of money, but Mr. Obama has exceeded expectations with his fundraising gains.

“The momentum is with the person who surprised you, not the one who met expectations,” he said.

The two other fund-raisers for Mr. Obama were hosted by a former owner of the New York Islanders, Steven Gluckstern, and Joan and George Hornig of the Upper East Side.

Mayor Bloomberg, who is considered a potential presidential candidate, praised Mr. Obama’s fund-raising abilities yesterday when asked about political fund-raising, and said: “There’s no evidence you can’t raise a lot of money if the public likes you.”

Meanwhile, Mr. Obama’s campaign said yesterday he would not attend a Democratic presidential primary debate in September co-sponsored by the Congressional Black Caucus Institute and Fox News. A campaign spokeswoman would not say why Mr. Obama is declining to go.

A blog on the Politico’s Web site reported that Mrs. Clinton and a former North Carolina senator, John Edwards, also would not participate.