Colorado Senate candidate Gardner pushes bipartisanship in ads aired as ballots start arriving

Republican Rep. Cory Gardner argued he would be more bipartisan than his opponent, Democratic Sen. Mark Udall, in a pair of ads released Wednesday as ballots began to land in mailboxes across Colorado.

Udall, a Democrat, and Gardner have been locked in a months-long, neck-and-neck battle over a seat that could determine which party controls the U.S. Senate. Gardner has tried to emphasize his youth and the need for a change in Washington, while Udall has gone after his challenger on women's issues and for his role in last year's government shutdown.

Colorado's Senate race is one of the most expensive and competitive contests in the country. Republicans need to net six Senate seats to win control of the chamber.

Gardner's new ads featured the congressman talking directly to the camera and amount to the campaign's closing argument. In one spot, amid a mountain backdrop, Gardner says Udall's "campaign has gotten too tired, and too mean" and contends he will call out his own Republican Party when it's wrong. In the second, Gardner says he works "across party lines" to help create energy jobs and that Udall "gives into partisanship and helps the president destroy energy jobs."

Also on Wednesday, the environmentalist group NextGen Climate announced it would run an unusual ad attacking Gardner. Running two minutes long and posing as an investigative news report, it slams Gardner for "posing" as a champion of renewable energy and actually being tied to oil and gas companies.

Both Gardner and Udall have largely sided with their respective parties in Congress, but each candidate is trying to convince Colorado voters he is independent and his foe a rank partisan. Gardner repeatedly cites a study saying Udall supported Obama's priorities 99 percent of the time in the Senate, while Udall cites another study saying Gardner to be the 10th most conservative Republican in the House of Representatives.

The two are scheduled to face off for their fifth and final debate Wednesday night. Ballots were mailed to voters on Tuesday.

Under Colorado's new election laws, which were approved by Democrats over Republican protests last year, citizens can register to vote and cast ballots up until Election Day. The system is believed to help the side with the best get-out-the-vote operation, an area where Democrats have excelled in Colorado.