Republican Dan Maes, who is running for governor in Colorado, lost an influential endorsement after the Denver Post questioned his claims that he worked as an "undercover" police officer 25 years ago.

Former Sen. Hank Brown (R-Colo.) had backed Maes but said on Wednesday he was withdrawing his support.

"I'm concerned about the revelations. I'm withdrawing my endorsement," Brown told the paper. "I'm beginning to find that [Maes’] explanations are not adequate."

Maes was already facing a threat to his right flank from Tom Tancredo. The former Republican congressman asked Maes to withdraw over his campaign finance violations, and when he refused, Tancredo entered the race as a third-party candidate.

According to the Post, the Maes website biography stated: "At one point in my 2 years there I was place (sic) undercover by the Kansas Bureau of Investigations (sic) to gather information inside a bookmaking ring that was also allegedly selling drugs. I got too close to some significant people in the community who were involved in these activities and abruptly was dismissed from my position. ... I was blindsided and stunned to say the least."

The Kansas Bureau of Investigation, however, said it has no record of Maes working with the agency during his service as a police officer from 1983 to 1985. The chief of police in Liberal, Kan., where Maes worked as a cop, did not remember his department ever being involved in the investigation Maes described in his biography. 

"Some people are probably taking that a little too literally," Maes said. "I was a city police officer providing information to the Kansas Bureau of Investigation."

But Maes admitted that he may have made some "incorrect comments."

Referring to his website biography, he said, "Whoever typed it, typed it. That's all I've got to say."

But Maes spokesman Nate Strauch later confirmed that Maes had written the comments.

Maes is up against Tancredo and Democrat John Hickenlooper in November.