Rep. Mike Simpson (R-Idaho), facing a tough primary fight from a Tea-Party-backed candidate, has been endorsed by the Chamber of Commerce.
Their primary has become a proxy battle for the broader civil war war between the establishment and conservative wings of the GOP. Simpson is a close ally of House Speaker John Boehner (R-Ohio), who has fundraised for him.
Simpson has long been attacked in his state for not being conservative enough and has faced primary challenges in the past, but none have been very well-funded.
This time around, however, Smith has the support of the deep-pocketed Club for Growth, a conservative group known to invest millions in races to sway the outcome.
The Chamber of Commerce will help counter any attacks from the Club.