(Reuters) - Republican voters in Georgia will choose their party’s nominee for governor on Tuesday in a two-man faceoff that has become a proxy battle between U.S. President Donald Trump and the state’s popular Republican governor, Nathan Deal.

FILE PHOTO: Georgia Secretary of State Brian Kemp speaks with visitors to the state capitol about the "SEC primary" involving a group of southern states voting next month, in Atlanta, Georgia, U.S. February 24, 2016. REUTERS/Letitia Stein/File Photo

In May, Lieutenant Governor Casey Cagle, who has Deal’s endorsement, finished ahead of Georgia Secretary of State Brian Kemp. But Kemp, whose hardline campaigning approach dovetails with Trump’s, earned the president’s backing last week, a surprise endorsement that should give him a major boost among Republican voters in the run-off election.

“I would think it does give the edge to Kemp,” said Charles Bullock, a political science professor at the University of Georgia.

Recent polls show a close race. The winner of Tuesday’s contest will face Democrat Stacey Abrams, who is vying to become the first black woman to serve as a U.S. state governor in what is expected to be one of the most hotly contested races in November’s midterm elections. Trump carried Georgia by five percentage points in 2016.

The Republican nominating race has been marked by fiercely negative campaigning.

FILE PHOTO: Georgia Secretary of State Brian Kemp speaks with visitors to the state capitol about the "SEC primary" involving a group of southern states voting next month in Atlanta, Georgia, U.S., February 24, 2016. REUTERS/Letitia Stein/File Photo

Cagle, 52, bested Kemp, 55, by 13 points in the springtime primary to set up the top-two showdown. But he came under fire in recent weeks after Kemp and another candidate who finished fourth released secret recordings in which Cagle acknowledged supporting a bad policy for political reasons and said the primary appeared to be a contest to see who could be “craziest.”

That last comment likely referred to Kemp’s political advertisements, in which he jokingly threatened a teenage boy who wanted to date his daughter with a shotgun and promised to “round up” illegal immigrants in his truck.

Deal, who cannot run again due to term limits, endorsed Cagle last week, a move countered two days later when Trump posted his support for Kemp on Twitter.

“Today is the day to vote for Brian Kemp. Will be great for Georgia, full Endorsement!” Trump said in another tweet on Tuesday, three days after Vice President Mike Pence campaigned with Kemp.

Kemp tweeted a photo of Trump on Tuesday morning, saying he would “unapologetically stand” with the president. Cagle, meanwhile, wrote on Twitter, “We need a leader who is a bulldog for GA not a lapdog for D.C.”

Both candidates have embraced Trump and have similar policy positions, including support for gun rights, lower taxes and tough anti-illegal immigration measures.

Reporting by Joseph Ax; Editing by Colleen Jenkins and Bernadette Baum

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