Former President Donald Trump gestures during a campaign rally in St. Cloud, Minn., on Saturday, July 27, 2024.ALEX WROBLEWSKI/AFP via Getty Images

Arizona voters who take their cues from former President Donald Trump may have trouble choosing a candidate in Tuesday's Republican primary for an open congressional seat — because Trump is backing two of them.

But the highly unusual move could backfire on both men and help one of their rivals in the closely watched, five-way race, the Arizona Republic reported Tuesday.

In December, Trump endorsed failed state attorney general candidate Abe Hamadeh to replace outgoing Republican U.S. Rep. Debbie Lesko.

But on Sunday, Trump announced he was also endorsing Blake Masters, who he'd previously backed during Masters' losing 2022 bid for U.S. Senate against Democrat Mark Kelly, now reportedly under consideration to be Vice President Kamala Harris' White House running mate.

"They will both be spectacular, and I'm pleased to announce that both Blake Masters and Abe Hamadeh have my Complete and Total Endorsement to be the next Congressman of Arizona's 8th Congressional District - THEY WILL NOT LET YOU DOWN!" Trump wrote on his Truth Social website.

The 11th-hour move came after Trump earlier this month named freshman Republican Ohio Sen. J.D. Vance as his running mate in the presidential race.

Both Vance and Masters have deep ties to tech billionaire Peter Thiel, who provided the bulk of the funding for their Senate campaigns two years ago.

Trump's dual endorsement "is a July surprise that changes the election" and could help state House Speaker Ben Toma and former U.S Rep. Trent Franks, Arizona GOP political strategist Barrett Marson told the Arizona Republic.

"It's late but not TOO late," Marson said. "Splitting the Trump-centric vote opens the door for both Ben Toma and even Trent Franks."

Fewer than half of the district's Republicans who requested early ballots had voted as of Monday and those most likely to go the polls Tuesday will be ardent Trump supporters, according to the Republic.