He and Sen. Jon Tester (D-Mont.) are locked in a tight race where each has sought to paint the other as a creature of Washington.
"Someone might want to tell Senator Tester's liberal Washington backers that Tester is the number-one recipient of lobbyist campaign cash in Congress this election cycle, and he's literally made headlines for doing the bidding of Wall Street bankers and lobbyists, then filling his campaign coffers with their money," Rehberg spokesman Chris Bond said in a statement. "In reality, Jon Tester loves lobbyists, and it's clear from their decision to shower him with cash that lobbyists love Jon Tester right back."
The National Republican Senatorial Committee is also out with a new ad saying Tester "broke his promise to Montana" by voting with President Obama and "sold Montana out" by voting to reinstate the inheritance tax. Watch the ad here:
This post was updated at 11:40 a.m.