The League of Conservation Voters and its state subsidiary are launching a radio ad against Rep. Denny Rehberg (R-Mont.), who is challenging Sen. Jon Tester (D), for taking “$460,000 from dirty energy companies” while voting to “block the enforcement of a vital mercury pollution law.”

Montana Conservation Voters Executive Director Theresa Keaveny said in a statement that it is “simply wrong for politicians like Representative Rehberg to interfere by blocking scientists at the [Environmental Protection Agency] from” setting air pollution limits.

The ad is set to run in the Billings and Kalispell media markets.