The Senate Conservatives Fund, a group that has been wading more deeply into Republican primaries lately, on Monday added retired U.S. Air Force Col. Rob Maness (R) of Louisiana to the roster of candidates it is backing.

"Colonel Rob Maness is a constitutional conservative with a remarkable record of service to our country," Senate Conservatives Fund Executive Director Matt Hoskins said in a statement. "He understands the value of our freedoms and will fight to repeal Obamacare and stop the massive spending, bailouts, and debt that are bankrupting our country."

Started by Jim DeMint during his days as a South Carolina senator, the group has often butted heads with establishment Republicans with whom it has been at odds in some Senate races over the years.

Maness is an underdog to Rep. Bill Cassidy (R) in the race for the GOP nod in Louisiana's open primary. He's raised scant campaign cash compared to the congressman. Republicans are vying for a chance to run against Sen. Mary Landrieu (D), one of the most vulnerable senators up for reelection next year.

Maness, who is running to Cassidy's right, retired from active duty in 2011 after more than 32 years of service, according to his campaign Web site.