Sen. Mark UdallMark Emery UdallSenate GOP rejects Trump’s call to go big on gun legislation Democratic primary could upend bid for Colorado seat Picking 2018 candidates pits McConnell vs. GOP groups MORE (D-Colo.) is airing his first ad of his reelection fight, a negative spot that hits Republican opponent Rep. Cory GardnerCory Scott GardnerTrump makes Manchin top target for midterms Wyden: I object to Trump’s DHS cyber nomination over demands for Stingray information Trump’s confirmation chaos in perspective MORE on abortion and other women’s issues.

The ad declares that Gardner’s “history promoting harsh abortion laws is disturbing,” and highlights "personhood" measures he’s supported that would have given legal rights to a fertilized human egg, effectively outlawing abortion and certain forms of birth control.

Gardner has, since entering the race, shifted his position on those measures and now opposes them, but Udall’s campaign has continued to knock him on the issue because he remains a co-sponsor of federal personhood legislation.

“But Mark Udall protects our right to choose, our access to birth control,” a female narrator says in the ad. “Mark Udall, in a word: Respect.”

Democrats believe women's issues in particular will help them take down Gardner, who entered the race in February and gave Republicans a top-tier challenger in a race they see as competitive due to ObamaCare.

Gardner’s campaign blasted Udall for going negative, with his campaign manager Chris Hansen charging the senator is attacking Gardner because “he has no record of accomplishments."

”While Coloradans sound the call for new leadership, Sen. Udall continues to lie about Cory Gardner’s record while distorting his own,” Hansen added.

He went on to knock Udall on ObamaCare, declaring that "if Senator Udall trusts and respects women, and all Coloradans for that matter, then he should not have lied to them about keeping their healthcare plans and doctors."