WATCH: Cosby Featured in Montco Attack Ad

Kevin Steele, running for Montgomery County DA against Bruce Castor, says his opponent is "not looking out for the victims." Castor says Steele is "desperate."

A decision Bruce Castor made almost 10 years ago is the subject of a new attack ad. That decision: Not to prosecute Bill Cosby.

Andrea Constand, who worked at Temple at the time, told prosecutors in 2005 that Cosby drugged and sexually assaulted her at his Cheltenham home. Castor did not file charges. Constand later sued Cosby and reached a settlement in 2006.

Castor, a Republican and Montgomery County commissioner, was the county district attorney from 2000 to 2008. He’s running again for the seat this year. His opponent, Montco first assistant DA Kevin Steele, this week released an advertisement that attacks Castor for his decision on Cosby. (Cosby, it should be noted, has never been criminally charged nor convicted in any jurisdiction, and has denied the the accusations against him. He faces civil lawsuits from several women across the country, however.)

The ad highlights a quote Castor gave before deciding whether to charge Cosby. “In Pennsylvania, we charge people for criminal conduct,” he said at the time. “We don’t charge people for making a mistake or doing something foolish.”

The ad concludes: “Bruce Castor is not looking out for the victims.” Castor told NBC 10 the attack ad was “predictable craziness from a desperate candidate.”

Steele, a Democrat, and Castor are both running for the job currently held by Risa Vetri Ferman. She said earlier this year she would not run for a third term and is instead seeking a position as a county judge.

Castor said in July he would consider building a new criminal case against Cosby if it could be determined he lied under oath during the 2005 investigation.

Ten years ago, though, he said there wasn’t enough evidence to prosecute, adding Constand’s case was “weak.” He also said, before deciding not to charge Cosby, that Constand’s decision to come forward only after a long time had elapsed was a determining factor that helped Cosby. “I think the factors such as failure to disclose in a timely manner and contacts with the alleged perpetrator after the event are factors that weigh toward Mr. Cosby,” Castor said at a news conference in 2006.

Cosby’s reputation remained untarnished by the 2005 sexual assault allegations; he even collected an honorary degree from Oberlin five years after the allegations were made public. Since this time last year, after a video of comedian Hannibal Buress’ stand-up bit calling Cosby a rapist was published at Philadelphia magazine, many additional women have come forward with similar stories as Constand’s. Castor says now he wanted to prosecute Cosby, but didn’t have enough evidence.

A lawyer for Constand attacked Castor in an open letter to him. “We have watched you appear on various media outlets engaging in blatant revisionist history,” Dolores Troiani wrote. “We demand that you retract your statement concerning Ms. Constand and issue the apology to her that is 10 years overdue.”

Castor said he would not apologize to Constand. He continues to say the primary problem with the case was that Constand “delayed a year in reporting it.”