Rep. Cory GardnerCory GardnerTrump applauds congressional allies as he kicks off inaugural festivities Overnight Tech: Tech listens for clues at Sessions hearing | EU weighs expanding privacy rule | Senators blast Backpage execs Overnight Tech: Trump meets Alibaba founder | Uber to make some data public | GOP Lawmakers tapped for key tech panels MORE (R-Colo.) accused Sen. Mark UdallMark UdallLive coverage: Tillerson's hearing for State The rise and possible fall of the ‘Card’ in politics Gardner's chief of staff tapped for Senate GOP campaign director MORE (D-Colo.) of lying about ObamaCare.

Gardner is challenging Udall in the midterm election for Udall's Senate seat.

“Mark Udall promised if you liked your plan, you could keep your plan," Gardner said on Thursday. "Mark Udall promised if you liked your doctor, you could keep your doctor. Mark Udall lied to the people of Colorado.”

Gardner has used Udall’s vote for the Affordable Care Act, also known as ObamaCare, against Udall in previous ads.

In the latest ad, Gardner points out that more than 300,000 Coloradans received healthcare cancellation notices, but he doesn’t say how many of those people now have insurance through the healthcare exchange.

Udall is one of the more vulnerable incumbents in November’s midterm election. Republicans need to win six Senate seats to gain control of the chamber.