The U.S. Chamber of Commerce is launching ads for three Republicans preferred by the establishment, including Rep. Mike SimpsonMIchael (Mike) Keith SimpsonHouse retirement sets off scramble for coveted chairmanship The Hill's 12:30 Report Even some conservatives seem open to return to earmarks MORE (R-Idaho), who is facing a Tea Party challenger backed by national conservative groups.

The move is the latest sign the Chamber plans to go toe-to-toe with groups like the Club for Growth and Madison Project, which are backing Simpson's opponent.

The Chamber is also running ads on behalf of Rep. Shelley Moore CapitoShelley Wellons Moore CapitoConway freezing out experts, relying on political staff in drug policy office: report Republican agenda clouded by division Fractured GOP struggles with immigration strategy MORE (R-W.Va.), the GOP front-runner to replace Sen. Jay Rockefeller (D-W.Va.) and Evan JenkinsEvan Hollin JenkinsWest Virginia rep joins in Manchin bash-fest These Democrats will have a hard time keeping their seats in 2018 Trump feud puts pressure on Bannon candidates MORE, a West Virginia lawmaker who switched from the Democratic Pasrty to Republican Party to challenge Rep. Nick Rahall (D-W.Va.).

"Mike Simpson: Conservative, Idaho strong," the ad for Simpson says. "Mike Simpson is fighting back, working for a balanced budget, reducing our dependence on foreign oil, fixing the Obamacare mess."

The Chamber has already stepped in to help a more centrist candidate this election, backing Bradley Byrne over Tea Party favorite Dean Young in an open-seat House election in Alabama. Its efforts to help ward off Tea Party candidates have intensified following last fall's government shutdown.

“With America’s job creators facing historic uncertainty, our number one focus is on jobs and growth. It’s time to get back on offense to get the economy moving again. Our efforts in Idaho are designed to back candidates who support American Free Enterprise and oppose those who stand in the way," says U.S. Chamber National Political Director Rob Engstrom.

The Club fired back against the ad for Simpson.

"It's no surprise that Mike Simpson is receiving support from his allies in Washington," said Club for Growth President Chris Chocola. "Mike Simpson supported the $700 billion bailout out of Wall Street. The Chamber of Commerce supported the $700 billion bailout of Wall Street. Mike Simpson supported keeping all the spending in the Obama stimulus. The Chamber of Commerce supported the Obama stimulus. Mike Simpson supported raising the debt limit by trillions of dollars. The Chamber of Commerce supported raising the debt limit by trillions of dollars.

"I guess pro-bailout, pro-Obama stimulus spending, pro-debt birds of a feather flock together."

This story was updated at 1:55 p.m.