After three months of quiet investigation, Montgomery County prosecutors could be weeks away from charging Bill Cosby with the 2004 sexual assault of a former Temple University employee, according to sources familiar with the probe.

The prosecution would revive a criminal case opened a decade ago. It would be the first against the actor-comedian, publicly accused of sexual misconduct by dozens of women nationwide.

But whether the case moves forward and in what form could hinge on the outcome of next week's election.

On Monday, the accuser, Andrea Constand, filed a defamation suit against former District Attorney Bruce L. Castor Jr., who declined to prosecute based on her allegations in 2005 and is running to reclaim his old seat.

Filed in federal court in Philadelphia, Constand's suit accuses Castor of publicly undermining her credibility, misstating facts about her case, and twisting her story to benefit his political ambitions.

Her lawyer, Dolores Troiani, acknowledged that Constand is cooperating with the probe, overseen by District Attorney Risa Vetri Ferman and Kevin Steele, her first assistant and Castor's opponent in the campaign. If Castor wins, she said, Constand will likely back out of the case.

"How can we possibly trust him?" Troiani said. "I don't know how we could possibly do that."

Castor accused Constand and Troiani of engaging in "quite despicable behavior," and called their lawsuit a bid to influence the election.

"It really is stunning to see the lengths that these people will go," he said. "I'm a lawyer. I'm not afraid of court. I think the people who filed this lawsuit ought to be afraid."

Ferman has declined to say whether her office has reopened its investigation into the claims Constand first lodged in 2005, when she told police that Cosby drugged and assaulted her at his Cheltenham mansion.

But sources said a revived investigation began this summer, after details of a deposition Cosby gave that year about his relationship with Constand became public.

Montgomery County investigators met with Constand again in August and have since interviewed individuals who were close to her or Cosby at the time of the alleged assault, said the sources, who declined to be named discussing an ongoing investigation.

Since then, the handling of Constand's claims then has emerged as a primary point of contention in the race between Castor, a Republican, and Steele, his Democratic opponent.

Last week, Steele's campaign began running ads challenging Castor's decision not to prosecute Cosby a decade ago. Castor responded with a similar ad questioning the lack of prosecution under Steele. He also has he would take a fresh look at the case if he were to win the election.

"I have said repeatedly and for months that if I ever get the opportunity where I get the power to review the investigation into Cosby, I would do so," Castor said last week.

In other interviews over the last year, he has repeatedly been asked to explain why he opted not to bring charges when he first had the chance, in 2005. Many times Castor said that the version of events Constand laid out for Cheltenham police varied significantly from the story she described that year in a lawsuit against the entertainer.

"That's not to say she lied in her civil suit," Castor said Monday. "Her lawyers wrote out allegations that they hoped to be able to prove in court. We have to worry about what we can prove beyond a reasonable doubt."

Troiani balked at that explanation of the events of a decade ago, saying that it implies Constand exaggerated or lied to collect a civil judgment. (Her lawsuit against Cosby was settled out of court.) Such suggestions could damage Constand's credibility should the criminal case against Cosby move forward.

Prosecutors have until January to file a criminal case based on her claims under Pennsylvania's 12-year statute of limitations for felony sexual crimes. Ferman, a Republican who once was Castor's first assistant and later named Steele to the same job, is completing her second term and hopes to win a judgeship next week. Castor is currently a Montgomery County commissioner.

Steele has declined to say what he would have done if he had been in Castor's shoes in 2005 or what he will do if wins next week.

"I'm confined on what I can say about a specific case," he said this month. "However, a case where there has been allegations of this nature needs to be looked at."

Still, Troiani maintained it was not Constand who turned her case into a political issue. Constand is seeking at least $300,000 in damages plus attorney's fees.

"We don't have a dog in this fight," Troiani said. "Whether or not they decide to prosecute Cosby is not our decision. This suit is not about that. He made this a political issue, and that's wrong. It's wrong for Andrea. It's wrong for Bill Cosby."


Inquirer staff writer Jessica Parks contributed to this article.