The suspected serial rapist linked by DNA to three sexual attacks on strangers — one of whom was a 13-year-old girl — also has close ties to some of the state’s high-profile Democratic politicos.

When William Costello was arrested in Bayfield on Nov. 5, he was volunteering to drop off yard signs at a Durango campaign office and was driving the car of a top political strategist, police records show.

Those who know Costello, 47, paint a picture of a successful real estate broker and dedicated father, someone trusted in the upper echelons of the community who gave no outward sign he could have committed such dark crimes.

Prosecutors have charged him with multiple counts of sexual assault, kidnapping and impersonating a police officer, according to affidavits released Monday.

The news astounded many respected members of the community, said former Gov. Dick Lamm, whose son befriended Costello when they attended Denver’s East High School together.

Lamm said that Costello had “slipped out of our lives” recently and that he last saw Costello at a birthday party for Lamm’s grandson three years ago.

“It just makes you shake your head,” Lamm said. “He was the kind of guy that mothers would be so pleased to see their daughters walk off with on a date. He was tied in with some very prominent Colorado names who mentored him. We are in shock around here.”

Lamm said Costello, as a young man, always seemed to be a go-getter, smart and articulate.

Costello doesn’t appear to have been politically active beyond volunteering on Democratic campaigns. Relatives and associates say he had been in custody disputes with the mother of his 6-year-old son and has been in a 2½ -year-long relationship with his current girlfriend.

No one who spoke to The Denver Post on Tuesday said they knew Costello to be aggressive or disrespectful toward women or — as is alleged in one affidavit — to carry a handgun.

It was go-to Democratic political consultant Mike Stratton’s new SUV that Costello was driving when the Bayfield Marshals and the FBI pulled him over the morning of Nov. 5.

Stratton, working from Pueblo, had dispatched Costello on a delivery run, he said. The SUV was impounded. Stratton was told there were “serious charges” against Costello but didn’t learn the details of the allegations until the affidavits were released.

“I’m just astounded, disgusted and saddened for his family. I don’t even have words for this,” said Stratton, who has known Costello “off and on over the years.”

The first time any law enforcement agency got to know Costello was July 30 in the parking lot of a Denver King Soopers. He allegedly assaulted an anti-abortion petitioner by shoving the man off his bike and breaking his hip after Costello “shouted obscenities” and “said he believes in abortion,” according to the affidavit.

Costello told authorities he grabbed a clipboard from the man so as not to be struck with it and the 69-year-old man fell. Costello faces a felony second-degree assault charge in that case.

Katie’s Law, which took effect late last year, requires police to take DNA samples from anyone charged with — not necessarily convicted of — a felony. Costello’s DNA matched samples found on the bodies and panties of sex assault victims in the three attacks dating back to 2008.

While many highly publicized serial rapes are committed by drifters and people with criminal records, Denver District Attorney Mitch Morrissey said there’s no standard profile for that type of sexual predator.

Morrissey was speaking generally — not about Costello’s case in particular.

“They used to say there’s the typical serial sex offender or serial murderer — that’s just not true,” Morrissey said. “Where DNA really, really makes its biggest impact is in stranger attacks. That’s the thing about Katie’s Law. It gets people into the database quickly.”

As of Monday, the Colorado Bureau of Investigation had recorded 75,007 DNA samples from individuals charged with felonies since Katie’s Law took effect. Those samples yielded 398 hits on unsolved cases, according to the agency’s statistics.

Morrissey said Costello’s is the most significant case possibly solved by the law. His spokeswoman on Tuesday withheld Costello’s booking photo so other jurisdictions can see whether the pattern in the three Denver cases matches any other unsolved rapes.

In affidavits, the two women say they were lured into a Mercedes-Benz sedan and described their attacker as a middle-aged, medium-build bald man wearing a baseball cap.

In the 2010 and 2011 attacks, he allegedly impersonated a police officer, threatening to arrest one woman unless she had sex with him.

In the first of Costello’s alleged attacks — on March 22, 2008 — he’s accused of luring a 13-year-old runaway into his car, driving to a secluded spot and raping her.

The girl told police there was a 2-year-old boy in the backseat.

Costello’s mother learned of the charges against her son through the media Monday. The allegations don’t match up with the “kind, creative and generous” man Gayle Costello knows. She said he suffered no abuse during his childhood.

She noted he has been stressed about the custody issues and the death of his father two years ago, with whom he was very close.

“We are all aghast. A mother could not ask for a more wonderful son,” said Gayle Costello, whose family’s roots in Colorado date back seven generations. “We love him very much. We support him no matter what. And we’re very sorry if he harmed anyone.”

Jessica Fender: 303-954-1244, jfender@denverpost.com or twitter.com/oh_fender