Mayor Bloomberg is 80% likely to launch a bid for the White House if the two major candidates come from the “extreme wings” of their party, one of his first-term advisers said.

The comment from a Columbia University professor, Ester Fuchs, keeps alive the notion that Mr. Bloomberg is mulling the possibility of entering the 2008 race even as the Democrats and Republicans who have already declared are traveling the country and campaigning.

According to ABC News, which reported the comment on its Web site, Ms. Fuchs said it was “80% probable” that Mr. Bloomberg would run as an independent if both major parties put up extreme candidates. She cited Senator Edwards, a Democrat, and Mitt Romney, a Republican and former governor of Massachusetts, as nominees who would make Mr. Bloomberg’s candidacy a possibility, ABC reported.

Ms. Fuchs could not be reached yesterday, but the director of ABC polling, Gary Langer, told The New York Sun that she made the comment Thursday evening while on a panel at Fordham University.

Mr. Bloomberg has said he is not interested in running, but he has also coyly noted that anyone planning to run would deny it until they were ready to announce. He has said he would make a good president.

Until now, one of Mr. Bloomberg’s deputy mayors, Kevin Sheekey, has taken the chief role of fanning the Bloomberg-for-president speculation. Having other allies such as Ms. Fuchs outline scenarios under which he would run adds credence to the idea that he is seriously considering the matter. It also helps keep him relevant during his second, and final, term as mayor.

A political science professor at the University of Virginia, Larry Sabato, said Mr. Bloomberg, a multi-billionaire, presents a highly unusual situation.

“If he were an ordinary elected official you would just dismiss it out of hand,” Mr. Sabato said. “But you can’t because he’s so wealthy. He’s worth so much money, he could outspend both of the majority party candidates without spending any time fund raising.”

He added, however, that a Bloomberg candidacy was a long shot because the major parties are not likely to nominate “extreme” candidates. He also noted that it would be a tough sell to get Americans to abandon their political parties and vote for an independent. A recent Quinnipiac University poll found that despite his high approval rating as mayor, 56% of New Yorkers said they would not vote for him if he ran for president; 35% said they would.

A spokesman for Mr. Bloomberg, Stuart Loeser, joked via e-mail: “When Ester went back to Columbia, Kevin Sheekey got her old spot in the bullpen. The mayor does not plan to run for president, but he does plan to replace that chair, since it seems to have given both its occupants ants in the pants.”