in crowded GOP Senate primaries in states such as Georgia and South Carolina because its supporters in those states haven't reached a consensus on whom to back, he said.

The May calendar is crowded with 11 state primaries. In several, the establishment-backed candidates have the edge.

Some examples:

• In Kentucky, GOP Senate Minority Leader Mitch McConnell is far outpacing Republican Matt Bevin in polling and political donations ahead of the May 20 primary. Bevin, who had the early backing of several Tea Party groups, has struggled to gain traction and recently was forced to apologize for giving a speech at a pro-cockfighting rally. Crossroads' Law sits on the board of a super PAC raising unlimited funds to help McConnell's re-election.

• In Georgia's Senate race, more moderate Republicans Rep. Jack Kingstonand former Dollar General CEO David Perdue lead in polling ahead of their more conservative rivals Reps. Phil Gingrey and Rep. Paul Broun, a physician who gained attention for calling evolution and the Big Bang theory "lies straight from the pit of hell."

The U.S. Chamber of Commerce's new ad touts Kingston as the "consistent conservative" in the race. The primary is May 20.

Broughton said the Tea Party Patriots may get involved if there is runoff in Georgia.

• The chamber also is working to serve as a financial counterweight to Tea Party groups in Idaho, where GOP Rep. Mike Simpson, a veteran House appropriator, is facing a primary challenge from businessman Bryan Smith. The chamber and other pro-business groups, such as the National Association of Realtors, have backed Simpson,