Scott M. Stringer May Drop Ambition for Mayor's Office Scott M. Stringer, the Manhattan borough president, is expected to announce soon that he will not run for mayor next year, but instead vie for city comptroller, according to half a dozen people who have talked to him in recent days. Mr. Stringer, a Democrat from the Upper West Side, had been trailing other likely contenders in early polls, and decided the math was insurmountable. "I'm sure it's hard, but the numbers haven't budged, and he didn't want to wait until it was too late," said one Democrat who, like all those who were interviewed, spoke on condition of anonymity so as not to antagonize Mr. Stringer or his allies. A spokesman for Mr. Stringer, George Arzt, declined to comment. If Mr. Stringer does opt out, his decision would be the first major shake-up in what is expected to be a wide-open race to succeed Mayor Michael R. Bloomberg. Such a decision would have a domino effect on other races, including the one for comptroller. Even though no Democrat has captured the mayoralty since 1989, many political analysts believe that whoever wins the Democratic primary next fall will be strongly favored to win. Those Democrats include Bill de Blasio, the public advocate; John C. Liu, the comptroller; Christine C. Quinn, the City Council speaker; and William C. Thompson Jr., a former comptroller. Several former Democrats are also likely to run on the Republican and Independence Party lines, including Adolfo Carrión Jr., a former Bronx borough president; Tom Allon, a newspaper publisher; and George T. McDonald, the founder of the Doe Fund.People who have talked to Mr. Stringer recently predicted that he would address the issue by early next week.