After months of speculation and rumors, Council Member David Yassky aborted his plan to run for Kings County district attorney yesterday and said he would try for re-election instead.

Mr. Yassky, who raised more than $750,000 for his district attorney bid, notified friends and supporters through a mass e-mail and phone calls throughout the day.

He told The New York Sun he believed new leadership was needed in the prosecutors’ office but it was simply “not the right time” for him to give up his council seat to make the run.

Though some have said private polls showed that it would have been difficult for him to knock out the incumbent, Charles Hynes, who was first elected in 1989 and is running for his fifth term, Mr.Yassky avoided that line of questioning yesterday, saying he had unfinished business in the council.

“The real truth is that I was just not ready to end my career in the council,” he said in a telephone interview. “Four years is not that long a time and there’s more I want to get done.”

When pressed, he said the bid for district attorney was “far from a sure thing” and it would have been a “risky” race.

Mr. Yassky’s withdrawal changes the political terrain for two races.

In the campaign for district attorney, it removes a formidable opponent for Mr. Hynes and the five other candidates who are planning to run.

Mr. Hynes, who had a scare in his last election when a little-known candidate, Sandra Roper, won 37% of the vote, sent out a statement by e-mail yesterday saying Mr. Yassky would have been a strong opponent. But he said: “In seeking another term in the city council he remains a strong advocate for Brooklyn.”

Some said Mr. Yassky’s decision could make the race trickier for the veteran district attorney because it provides one fewer candidate to split the anti-Hynes vote. Other challengers said their campaigns were still in gear. A former Koch administration official, Arnold Kriss, and State Senator John Sampson said they were continuing to raise money and were interviewing campaign managers. Others flirting with the idea of running are a former aide to Attorney General Eliot Spitzer, Mark Peters; a federal judge, Sterling Johnson; a Brooklyn lawyer, Paul Wooten, and Ms. Roper.

Mr. Hynes, who has faced criticism over his probe of Democratic leaders and his alleged selective prosecution of political enemies, has been campaigning aggressively.

Mr. Yassky’s decision also brings to a halt the race to replace him on the council in a district that includes Brooklyn Heights, DUMBO, and parts of Williamsburg.

At various points, as many as seven people were considering a run. All of the candidates reached last night by the Sun said they would terminate their campaigns.

“A lot of this business is about timing,” one of them, a co-district leader in Park Slope, Alan Fleishman, said.

“I think this race for DA would have been a difficult one for him,” Mr. Fleishman, who works in the city comptroller’s office, said. “He probably didn’t see any way he could win it.”

The president of the Brooklyn Chamber of Commerce, Kenneth Adams, who raised $51,000 for his bid for the 33rd District seat, said he was “disappointed” that he would not be running but would reconsider in four years when Mr. Yassky, who will presumably win his seat in November, would be forced out of the council by term limits.

And Mr. Fleishman’s counterpart in the 52nd Assembly District, Jo-Anne Simon, said she would continue building support.

“This is politics,” she said. “One never knows.”