The super PAC aligned with Speaker Paul Ryan, R-Wis., is purchasing $800,000 of television advertising on Montana television to boost the Republican candidate in a May 25 special election for a vacant House seat as the GOP moves to defend another front in the battle for control of Congress.

Beginning Friday, the Congressional Leadership Fund is airing a 30-second spot on broadcast and cable television in the Billings, Bozeman, Great Falls and Missoula media markets. The ad attacks Democrat Rob Quist, a musician who is running for Montana’s statewide, at-large House seat against Republican Greg Gianforte, the GOP nominee for governor last year.