Rep. Cory GardnerCory GardnerBiden administration reverses Trump changes it says 'undermined' conservation program Gardner to lead new GOP super PAC ahead of midterms OVERNIGHT ENERGY: Court rules against fast-track of Trump EPA's 'secret science' rule | Bureau of Land Management exodus: Agency lost 87 percent of staff in Trump HQ relocation | GM commits to electric light duty fleet by 2035 MORE (R-Colo.) accused Sen. Mark UdallMark Emery UdallKennedy apologizes for calling Haaland a 'whack job' OVERNIGHT ENERGY: Haaland courts moderates during tense confirmation hearing | GOP's Westerman looks to take on Democrats on climate change | White House urges passage of House public lands package Udalls: Haaland criticism motivated 'by something other than her record' MORE (D-Colo.) of lying about ObamaCare.

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

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“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.