Former House Speaker Newt Gingrich endorsed Sen. Lamar Alexander, R-Tenn., Thursday.
"We need Lamar's experience and shrewdness to fix Washington," Gingrich, a Georgia Republican and former presidential candidate, said in a statement released by the Alexander campaign.
Alexander, a second-term senator, is heavily favored to win his Republican primary on Aug. 7. Conservatives initially marked Alexander as a potential primary target in 2014, but top opposition never came close to materializing like some of his colleagues, for example Sen. Thad Cochran, R-Miss.
Alexander's most formidable challenger is state Rep. Joe Carr. He's received more attention in recent weeks after Dave Brat, a largely unknown college professor with little money in his campaign, defeated House Majority Leader Eric Cantor, R-Va., in a primary earlier this month.
Carr released his first ad Thursday, which will run statewide, attacking Alexander for supporting the immigration overhaul.
The ad buy is in the six figures, according to the campaign, and they plan to run it through the primary.
The race is rated Safe Republican by the Rothenberg Political Report/Roll Call.