Romney Plugs Establishment Candidate in Key GOP Primary

The U.S. Chamber of Commerce, which has launched an unprecedented effort to defend vulnerable pro-business incumbents in Republican primaries this year, is enlisting a big gun to boost its favored candidate in Idaho.

In a new Chamber ad, former presidential nominee Mitt Romney touts his support of Idaho Rep. Mike Simpson, an establishment Republican facing a difficult May 20 primary.

Romney endorsed Simpson last year, but this is his first foray into television ads in the 2014 cycle. “You can take it from me,” Romney says in the spot. “The conservative choice for Congress is Mike Simpson.” While the former Massachusetts governor wouldn’t normally be the ideal arbiter of conservatism is a red-state primary, Romney has special cachet in the eastern Idaho district, which has a high concentration of Mormons.

This is the third ad the Chamber has cut on behalf of Simpson. The incumbent is trying to fend off a challenge from Bryan Smith, an attorney who boasts the backing of the antitax Club for Growth. The Club is also spending heavily in the race—earlier this week, it released an ad of its own, slamming Simpson for backing the Wall Street bailout.

The district has long been viewed as ground zero for the national battle playing out between big business and the Tea Party in this year’s GOP primaries.