(CNN) Jeff Sessions put back on the red "Make America Great Again" hat. The door to Tommy Tuberville's campaign bus said "#MAGA." Bradley Byrne urged fans at the Alabama-LSU football game to raise the roof when President Donald Trump walked to his stadium seats.

For the former attorney general, former Auburn football coach and congressman, the Republican primary race for a US Senate seat in Alabama has come down to one "big thing," according to GOP Rep. Robert Aderholt. "Which candidate is going to support Trump's principles?"

Each Republican has jumped on his competitor's rare break from the President. A month before the 2016 election, as Trump came under widespread criticism for bragging about groping women, Byrne said Trump "is not fit to be President." In 2019, Tuberville said he was "pissed off" at Trump because military veterans "can't get health care." And most famously, Trump publicly mocked and ultimately fired Sessions after he recused himself from overseeing the Department of Justice investigation into Russian interference of the 2016 election because he served on the Trump campaign.

But Sessions, who held this US Senate seat for 20 years before joining the Trump administration, is expected to emerge on Tuesday as one of two candidates in the fierce runoff election held on March 31. The winner of that race will then face Democratic Sen. Doug Jones in November, the best pickup opportunity for Republicans in the Senate.

"Senator Sessions is a known commodity, who has a great deal of personal integrity and people recognize that," Alabama Secretary of State John Merrill told CNN. "They're going to respond to him like they have before."

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