DENVER — Thursday marked the first time that the top Democratic and Republican candidates in Colorado’s Senate race appeared on the same stage for a debate, but former Lt. Gov. Jane Norton (R) was determined to keep the focus on the increasingly nasty GOP primary.

As Thursday’s breakfast event got under way at the Denver Center for the Performing Arts, Norton released a new commercial slamming Weld County District Attorney Ken Buck (R) for a recent comment he made about his choice of footwear.

“Why should you vote for me? Because I do not wear high heels,” Buck says in a video clip used in the ad. “I have cowboy boots. They have real bullshit. That’s Weld County bullshit.”

“Now Ken Buck wants to go to Washington,” a narrator says. “He’d fit right in.”

Norton’s camp is clearly hoping voters view Buck’s comments as sexist and that they will give voters pause during the final two weeks of the campaign. Her commercial was the subject of a good part of both candidate’s post-debate interviews.

Buck said the statement that was caught on tape at a campaign stop was merely a humorous response to a question from a woman who asked why she should vote for him. He pointed out Thursday that Norton had previously mentioned her high heels in a lighthearted way. But the video clip has gone viral in Colorado political circles in the past two days and Norton, who has trailed in most polls, sees the comment as a late opportunity.

“Integrity and character matter,” Norton said after Thursday’s debate. “I’d like people to look at the ad and decide for themselves.”

Buck, who had yet to see the ad Thursday morning, said Norton had “gotten desperate and run a lot of negative ads” in recent weeks.

“We need to get away from the nonsense” and focus on issues that matter, Buck said.

Many of those more traditional issues, from the economy to health care and immigration, were discussed by the Senate candidates and the top gubernatorial hopefuls at Thursday’s forum sponsored by ColoradoBiz magazine.

During the debate, former state Speaker Andrew Romanoff, who trails appointed Sen. Michael Bennet in most public polling on the Democratic primary, faced Bennet surrogate and former Denver Mayor Wellington Webb because the Senator skipped the forum to attend votes on Capitol Hill.

Some Democratic observers believe that Romanoff has yet to gain traction in the primary, despite some excitement in late June over an endorsement from former President Bill Clinton. In his lone television commercial so far, Romanoff slammed the Senator for taking special interest money. On Thursday, he worked to portray himself as a Washington outsider.

“If you like the way Washington works, you should vote for somebody else,” Romanoff said. “I am not satisfied with the pace of progress we’re making on Capitol Hill. That’s why I’m running for the Senate.”

Bennet, who was appointed in January 2009, has spent hundreds of thousands of dollars on a series of campaign ads that have portrayed him as a Senator who has shunned the intrigues of the Washington establishment during his short time there.

Webb worked to downplay Bennet’s Washington, D.C., connections on Thursday, a move that could be seen in his insistence on referring to his candidate as simply “Michael” instead of Sen. Bennet.

“We all know Washington is a mess today, completely detached from reality,” Webb said. “Michael hasn’t been in the Senate that long so most of this has preceded him. [But] in the time he’s been in the Senate, he’s been a reformer.”