Rep. Jack KingstonJohon (Jack) Heddens KingstonDan Rather: The voice of Florida survivors will change status quo Shooting survivors push for action in Trump meeting Rubio: 'Disgusting group of idiots' made up claim that shooting survivors are actors MORE (R-Ga.) has won the backing of former rival Rep. Phil GingreyJohn (Phil) Phillip Gingrey2017's top health care stories, from ObamaCare to opioids Beating the drum on healthcare Former GOP chairman joins K Street MORE (R-Ga.) in the runoff election for Georgia's GOP Senate primary.

Kingston is taking on businessman David Perdue (R) in the runoff on July 22.

Perdue won the May primary with 31 percent of the vote, while Kingston finished second with 26 percent.

Gingrey, who finished fourth with 10 percent of the vote, joins third-place finisher and former Georgia Secretary of State Karen Handel (R) in endorsing Kingston. Handel won 22 percent of the vote in May.

"Through the years Jack Kingston and I have been colleagues — and more importantly friends — he has been a relentless advocate for our shared conservative principles," Gingrey said in a statement released by Kingston's campaign. "Today I am proud to announce my support for Jack to be our next United States senator from the great state of Georgia."

Kingston has had some momentum since May. He's locked in more endorsements and led Perdue in the first poll of the race.

The winner of the July runoff will face former charity executive Michelle Nunn (D) in the fall.