The U.S. Chamber of Commerce waded into the Republican Senate primary Monday, choosing former Lt. Gov. Jane Norton over lawyer Ken Buck.

Two out of three voter surveys conducted this month found Norton trailing Buck, whose campaign has been getting significant backup from commercials being run by the group Americans for Job Security.

The state party’s conservative wing is solidly in Buck’s corner — so much so that Norton skipped the GOP convention and used the petition route to get her name on the ballot.