Assemblyman Richard Brodsky’s decision to donate a kidney to his daughter, Julianne Willie, has narrowed the Democratic primary field in the state attorney general’s race.

The surgery will take place within 90 days, and the recovery period could last for five weeks, Mr. Brodsky said.

While citing the surgery as the reason for his withdrawal, Mr. Brodsky told The New York Sun he is now “inclined” to seek re-election to the Assembly seat representing Westchester he’s held since 1982. A Westchester County legislator, Tom Abinanti, is running for that seat. He refused to say if he would stay in the race.

In January, Mr. Brodsky’s campaign had $1.2 million on hand, according to the latest campaign filing. Contributions to Mr. Brodsky’s attorney general’ campaign that do not exceed the Assembly campaign contribution limit can be used in the Assembly race, a state Board of Elections spokesman said.

“Willie’s transplant is necessary because of an auto-immune disease,” the family’s doctor, Robert Weiss, said in a public statement. “It is always difficult to predict how long an affected kidney will be functional in these circumstances.” When asked, Mr. Brodsky said, “you never know” if his daughter will need another transplant. Mr. Brodsky’s kidney will replace one his wife, Paige, donated to their youngest daughter 11 years ago.

An alternative treatment was discouraged. “I explained that there is always an option of using dialysis, although I did not recommend it,” Dr, Weiss said. “Willie is a healthy, vibrant teenager and this transplant will keep her just that way, and even make her life a little easier.”

“This happens to families every day, and we’re going to get through the way they get through,” Mr. Brodsky said. “We’re very lucky, that we have people who are able to do this.”

Last week, Mr. Brodsky turned 60 and announced plans for a statewide listening tour that would start on Long Island and end in Buffalo in time for the state party’s nominating convention.

Mr. Brodsky’s withdrawal Thursday drew praise from his five rivals, who stepped up their campaign intensity in recent days.

“As a father of three girls, I can hardly imagine how difficult this time must be, and I know Richard puts his family ahead of everything else,” the frontrunner, Andrew Cuomo, said.

Also running are a former public advocate, Mark Green, attorney Charlie King, a former federal prosecutor, Denise O’Donnell, and a former White House aide, Sean Patrick Maloney.