Trailing Senator Clinton in the race for campaign cash, Senator Obama is sweeping through New York City for a flurry of fundraising events on Thursday, one of which will be hosted by a Republican-turned-Democrat and another by a couple hosting their first political fund-raiser.

Mr. Obama will top off his fundraising frenzy with his first campaign visit to Harlem, where he will deliver a speech at the Apollo Theater, where the doors will open at 7:00 p.m. The Obama campaign is aiming to sell out the 1,500-seat landmark, where tickets are $50 each, and send a message that Mr. Obama is intent on running a competitive race in Mrs. Clinton’s home state.

Mr. Obama is expected to appear at a total of five events on Thursday, beginning with a morning breakfast at Credit Suisse First Boston and then a second breakfast at the Upper West Side home of Susan Waterfall, where guests will pay $2,300 to attend.

Until about two months ago Ms. Waterfall was a registered Republican who voted twice for President Bush and donated $2,300 to Mayor Giuliani in March. She said she became a Democrat so she could vote for Mr. Obama in the primary. Ms. Waterfall donated $2,300 to Mr. Obama in May and said she feels “very strongly that he would be the best president to lead our country.”

Ms. Waterfall is the director of marketing at a New York investment firm, and her apartment on the 14th floor of the Beresford on Central Park West and 81st Street overlooks Central Park.

This is the first time she has hosted a fund-raiser for Mr. Obama.

Later in the day, Mr. Obama will travel to the home of Virginia Davies and her husband, Willard Taylor, attorneys who live on West 12th Street and Eighth Avenue, for an evening reception where tickets are $1,000 and $2,300, and young professionals will be asked to pay what they can afford, Ms. Davies said.

Ms. Davies said the reception is the first political fund-raiser she and her husband have held. She said Mr. Obama could lead the Democratic Party, and “more importantly, the country” to bring about needed change. Support for him is growing in New York, she said.

“I think he has tremendous momentum, and it’s building. And just you wait till after Iowa,” she said.

Mr. Obama is expected to travel to the Hamilton Heights neighborhood of Harlem for a 7 p.m. fund-raiser at the home of a former president of the Apollo Theater Foundation, Derek Johnson, and his wife, Susan, on Hamilton Terrace. Tickets to the private event are $500–$5,000.

In a feat of planning common during presidential campaigns, Mr. Obama has back-to-back evening events on Thursday, with two fund-raisers that directly overlap.