"In Montana your word is your bond — unless you're Congressman Dennis Rehberg," the ad intones before playing a clip of Rehberg promising to "never support nor take a pay raise."
Democrats have sought to highlight Rehberg's time in Washington as well as his personal wealth in the populist state. The DSCC did not disclose how much money is behind the ad.
Rehberg's campaign fired back.
"Clearly Tester's liberal Washington strategists have a tough job trying to distract Montanans from his 95 percent support of Obama's unpopular agenda, and that's why they're making these desperate attacks," said Rehberg spokesman Chris Bond. "Someone should tell them Tester voted to raise his own pay in both the Montana Senate and the U.S. Senate, and while they're at it, maybe they'd like to explain Tester's 55 votes for higher taxes, his votes for Obama's anti-gun Supreme Court judges, his deciding 60th vote for Obama's health care law, and his support for Obama's tax-and-spend economic policies."
The ad's release comes on the same day that Sen. Jon Tester (D-Mont.) launched an ad highlighting his independent streak. The two are locked in a tight race in the GOP-leaning state.
This post was updated at 2:20 p.m.