Throughout his career, Mr. Obama has enjoyed close ties to Jews, including various employers, law school buddies, wealthy donors on the north side of Chicago who backed his early political career, and the many Jews in the Hyde Park community where he lives. This may account for some of Mr. Obama’s apparent incredulity at the way some Jewish voters view him.

“I’ve been in the foxhole with my Jewish friends, so when I find on the national level my commitment being questioned, it’s curious,” he said recently in an interview with Jeffrey Goldberg on theatlantic.com.

Now the half-Kenyan-by-way-of-Hawaii candidate, who only recently completed a beer-and-bowling tour to impress blue-collar Midwesterners, has committed more fully to showing off his inner Jew. He recently made a surprise speech at the Israeli Embassy in Washington, and, in the interview with Mr. Goldberg, he told stories about a long-lost Jewish summer camp counselor who taught him about Israel and recalled reading Leon Uris and Philip Roth, arguably opposite poles of American-Jewish fiction.

Aides say Mr. Obama will spend as much time in South Florida as possible in the coming months. His aides believe that the negative rumors floating around about him are mere “noise,” as one put it, and have had little impact.

His aides also expressed confidence that when Mr. Obama officially becomes the nominee, the Democratic Party, including its many prominent Jews, will put their full force behind his efforts in Florida.

In anticipation, Mr. Obama has lined up surrogates like State Representative Dan Gelber, the House minority leader, and Mr. Wexler, both of whom are Jewish. Mr. Wexler said he would try to convert voters one mah-jongg table at a time, with town-hall meetings in the card rooms of high-rise condominiums and articles in community newspapers.

“Many of the political leaders in Palm Beach and Broward County were at my son’s bris,” he said.

Mr. Wexler said he had constituents who voted for Al Smith, the first Catholic presidential nominee, in 1928, “and they’ve never voted for a Republican since.”

“They are not going to vote for Senator John McCain,” he added.

Still, Mr. Wexler admits, he has not yet been able to persuade his in-laws to vote for Mr. Obama.