A conservative group is attacking Rep. Bruce BraleyBruce Lowell BraleyOPINION | Tax reform, not Trump-McConnell feuds, will make 2018 a win for GOP Ten years later, House Dems reunite and look forward Trump: Ernst wanted 'more seasoning' before entertaining VP offer MORE (D-Iowa) for his poor attendance of the Veterans Affairs Committee hearings.

Concerned Veterans for America, a group backed by the conservative billionaire Koch brothers, slams Braley in a new TV ad for missing three quarters of the full committee's hearings during the last Congress.

"The VA is failing our veterans. Secret lists, long waits, preventable deaths. Congress was warned but Bruce Braley ignored it. He skipped an astonishing 79 percent of Veterans Affairs Committee hearings," the ad's narrator says. "He even skipped an important VA reform hearing to attend three fundraisers. When our veterans needed him, Bruce Braley was AWOL. Tell Bruce Braley, reform and fix the VA."

Braley has been taking heat for the missed committee hearings in the state in what's turned into a coin-flip race against Iowa state Sen. Joni Ernst (R).

Braley's campaign fired back.

"It's insulting that the oil billionaire Koch brothers are trying to play politics with our veterans and distort the real and personal impact Bruce Braley has had on the lives of thousands of veterans in Iowa and across the nation,” said Iowa state Rep. Todd Pritchard (D), an Army reservist and Braley ally. "Bruce Braley's number one priority is delivering results for Iowa veterans—and I know firsthand that he has the record to prove it."

This post was updated at 2:10 p.m.