Rep. Mike Simpson, R-Idaho, got a boost from the Chamber of Commerce today when it officially released an ad in which former Republican presidential candidate Mitt Romney endorsed him.

Why Romney? Well, it may have something to do with the fact that Idaho is second only to Utah in number of Mormon residents. A full 24 percent of its population belongs to The Church of Jesus Christ of Latter-Day Saints, according to a Gallup study out last month.

In the ad, Romney touts Simpson as "the conservative choice" and says: "Mike is fighting hard every day to cut Washington's wasteful spending, to stop junk lawsuits and to fight against Obamacare."

Simpson is running in a tight primary against Bryan Smith, a lawyer backed by the Club for Growth and other groups associated with the Tea Party movement who don't view him a good on cutting spending. Simpson's congressional voting record earned him a 57 percent lifetime rating from the Club.