PHILADELPHIA >> A career prosecutor was ahead late Tuesday in a race for district attorney in suburban Philadelphia in an election that could lead to criminal charges being filed against Bill Cosby.

With 80 percent of precincts reporting, Democrat Kevin Steele had 54 percent of the vote.

If Steele wins, he will lead the Montgomery County office that’s reopened a 2005 sexual-assault complaint filed against Cosby. Prosecutors have until January to file charges in the 2004 encounter at Cosby’s gated home near Philadelphia.

The investigation is expected to end if Republican opponent Bruce L. Castor Jr. wins and returns as district attorney. Castor declined to charge Cosby a decade ago and has questioned the accuser’s credibility.

Steele, a deputy prosecutor, has been involved in a renewed investigation.

The Cosby case became a hot-button issue in the race amid news that the investigation had been reopened before the deadline to file charges expires. Cosby’s accuser has sued Castor, and her lawyer has said she will stop cooperating with law enforcement if he is elected.

The accuser, former Temple University employee Andrea Constand, filed a police complaint in 2005 saying Cosby had drugged and assaulted her at his Montgomery County home the year before. At the time, Castor announced he would not charge Cosby, saying both parties could be portrayed in “a less than flattering light.”

Later that year, Constand settled a civil lawsuit with Cosby for an undisclosed sum soon after he was forced to give a deposition. During the deposition, released this year, Cosby acknowledged a series of sexual relationships with young women, including some who now allege they were drugged and assaulted. The comedian, who starred as Dr. Cliff Huxtable on “The Cosby Show” from 1984 to 1992 and has been married for decades, called all the sexual activity consensual.

Castor has said that Constand described a more serious sex crime in the lawsuit than she told police.

Constand, of Toronto, filed a defamation lawsuit against Castor last month, accusing him of making her “collateral damage for his political ambitions.”

The current district attorney and Steele’s boss, Risa Vetri Ferman, decided to leave office to run for judge. She has declined to discuss the renewed investigation, but she issued a statement praising sex-assault victims for having the courage to come forward.

She and Steele, her top deputy, are leading the new investigation of Cosby. Two months ago, county detectives went to Canada to re-interview Constand.

Steele has used the Cosby case to question Castor’s judgment.

“Bruce Castor had an opportunity to bring charges, and he failed to do so,” he said in a 30-second ad that debuted two weeks before the election.

Castor’s office had interviewed a few women who came out early to support Constand and to say that Cosby had also assaulted them. But Castor, who was district attorney from 2000 to 2008, said he could not have known that dozens of women would ultimately step forward.

“The information about all of Cosby’s alleged victims came to light after I left the D.A.’s office,” Castor said. “Now the election rolls around and somehow it’s my fault?”