Former Queens Borough president Donald Manes, a chief target in a major federal corruption investigation here, committed suicide tonight by stabbing himself in the heart with a kitchen knife, police said.

Manes, 52, was pronounced dead at 11:15 p.m. at Booth Memorial Hospital after attempts to revive him failed.

In a dramatic news conference, Police Commissioner Benjamin Ward said that Manes and his wife Marlene had gone to dinner at Manes' sister's house and had returned to their home in Forest Hills, Queens, at 9:15 p.m.

According to his wife, Manes had been despondent throughout the evening, Ward said. After returning home, he was talking to his psychiatrist on the kitchen telephone when his daughter noticed him reaching into a drawer "in an erratic manner," Ward said.

Ward said Manes' daughter went to fetch her mother, but when Mrs. Manes arrived she found her husband on the floor with a knife in his chest.

She removed the knife and called police, Ward said. The emergency call was received at 9:53 p.m. Two police officers arrived at 10:15. Manes had no vital signs, Ward said. He was given emergency resuscitation on the way to the hospital.

The suicide is the latest development in the widening corruption scandal that became public after Manes attempted suicide on Jan. 10.

He was then the chief executive officer and head of the Democratic Party in Queens, a county of 1.9 million people. A close ally of Mayor Edward I. Koch, Manes was considered one of the three or four most powerful politicians in the city.

On Monday, Geoffrey Lindenauer, former deputy director of the city's Parking Violations Bureau, pleaded guilty to two counts of racketeering and mail fraud and admitted to accepting more than $410,000 in bribes from collection agencies doing business with the city. As part of an elaborate plea agreement with U.S. Attorney Rudolph Giuliani, Lindenauer had agreed to testify against Manes and other corruption suspects.

Lindenauer was a protege of Manes. One of the collection agency owners, attorney Michael Dowd, told federal prosecutors several weeks ago that Manes had told him to pay bribes to Lindenauer.

Manes' death could leave many unanswered questions, including one foremost in the minds of many New Yorkers: whether Koch knew about Manes' activities. A New York Times/CBS poll published today found that 53 percent of New Yorkers believe Koch knew about corruption in his administration.