Former US attorney general Jeff Sessions. — AFP/VNA Photo

WASHINGTON — Former US attorney general Jeff Sessions's political comeback screeched to a halt in Alabama Tuesday when he lost his bid to reclaim his old Senate seat to a political novice who earned President Donald Trump's endorsement.

The defeat is almost certainly a career-ender for Sessions, who emerged as a critical Trump ally after becoming the first US senator to endorse the brash billionaire in 2015, when he donned a red "Make America Great Again" cap and embraced the unlikely candidate on a campaign stage.

After being appointed to the cabinet as attorney general, he was sacked in late 2018 and won Trump's everlasting disdain.

With 91 per cent of Alabama precincts counted, former Auburn University football coach Tommy Tuberville was leading the Republican runoff with 61 per cent of the vote. The New York Times, CNN and other US media called the race for Tuberville.

The showdown in the deep-red southern state was seen as a test of Trump's influence over his core supporters amid broad frustration with his bungled response to the coronavirus pandemic and his handling of protests against racial injustice.

Both candidates claimed to be fervent allies of Trump. But while Sessions adhered to conservative principles and several tenets of Trumpism, the president never forgave him for recusing himself in 2017 from the probe into Russia's election meddling.

With Alabama passionately pro-Trump, the president inserted himself squarely into the race, badgering Sessions in recent weeks as a "disaster" of an attorney general who was unwelcome back in Washington, and touting Tuberville as a breath of fresh air.

"Tommy Tuberville WON big against Jeff Sessions," Trump tweeted late Tuesday. "Will be a GREAT Senator for the incredible people of Alabama."

Tuberville, 65, now heads to the November election to face Senator Doug Jones.

Jones is easily the most imperilled Democrat in the 2020 election cycle, but the party has expressed hope that strong anti-Trump sentiment this year could help them reclaim control of the Senate.

Trump in his tweet blasted Jones as a "super liberal puppet" of Senate Minority Leader Chuck Schumer and House Speaker Nancy Pelosi.

Tuberville painted Sessions as a weak candidate who "wasn't man enough to stand with President Trump when things got tough."

Sessions, 73, argued that Tuberville only recently moved to Alabama and lacks conservative convictions.

But Sessions's conservative bona fides were not enough to overcome Alabama Republicans' allegiance to the man in the White House.

Primaries were also held Tuesday in Maine and Texas, where Democrats were deciding who will challenge the Republican senators from those states. — AFP