Citizens United is endorsing Rep. Paul Broun (R-Ga.) in the crowded Georgia Senate primary.
The nod from the conservative group will give the Tea Party favorite a boost — and establishment Republicans new reason to be concerned about the race.
Establishment Republicans have publicly fretted about Broun winning the primary, fearing he might not be the party's best candidate in a general election.
Democrats have a strong recruit in former charity executive Michelle Nunn (D), the daughter of ex-Sen. Sam Nunn (D-Ga.), and are hopeful a messy Republican primary could give them a chance at winning the contest.
The seat is currently held by Sen. Saxby Chambliss (R-Ga.), who is retiring.
A win by Democrats in Georgia would make it much tougher for Republicans to win back the Senate in 2014.
Citizens United is giving Broun $15,000 for the race — $5,000 each for the primary, primary runoff and general election, the maximum allowed under the law. It called Broun the "only true conservative" running in the primary.
"To put it frankly, Dr. Paul Broun has a steel spine and will not waiver on conservative issues where others might bend," said Citizens United President David Bossie in the endorsement. "Dr. Broun is the best candidate for the job, and I am proud to support a patriot who will take on the Washington establishment in the United States Senate."
While the endorsement helps Broun, it's unclear whether he'll have enough money to compete in the race.
Rep. Jack Kingston's (R-Ga.) campaign announced Tuesday that he raised $800,000 in the fundraising quarter, a good figure for a contested primary, and now has $2.9 million cash on hand.
Broun is seeking to paint himself as the true conservative in a field of five GOP candidates, and the endorsement might help cement him as the Tea Party's choice in the primary, something that might bring other conservative groups behind him.
The deep-pocketed Club for Growth is the biggest financial player with interest in the race, and Broun has long been a favorite of the group.
The other Republicans in the race are: Rep. Phil Gingrey, former Georgia Secretary of State Karen Handel and businessman David Perdue.