WASHINGTON (AP) _ Maurice Turner, a former District of Columbia police chief and mayoral candidate, died Wednesday from complications following heart surgery. He was 57.

Turner had been hospitalized since May 11 after suffering a stroke. He suffered a second stroke, then underwent heart surgery May 17 to replace an infected heart valve that had caused the strokes.

Turner retired from the police department in 1989 after 32 years on the force, the last eight as chief.

He switched from the Democratic to the Republican Party, drawing public support from President Bush, but was defeated in the 1990 mayoral election by Democrat Sharon Pratt Kelly.

The drug trade, bolstered by the introduction of crack cocaine, exploded during the late 1980s when Turner served as chief. Several of his programs, including ''Operation Clean Sweep'' which aimed at arresting large numbers of people at open-air drug markets, were considered controversial at the time.