MONTGOMERY, Ala. (AP) — President Donald Trump’s endorsement of Jeff Sessions’ rival in the U.S. Senate race in Alabama is a blow to the former attorney general — once beloved but later scorned by Trump — as he attempts a political comeback in the state where he was for years a conservative icon.

The president's backing of his rival puts back at front and center the issue of Sessions didn't want to be a focus of the race: His falling out with Trump.

“It’s the campaign equivalent of dropping a nuclear weapon on Sessions,” said Alabama-based political consultant David Mowery, noting Trump remains extremely popular with Alabama Republicans.

Trump on Tuesday tweeted his support for former Auburn University football coach Tommy Tuberville in this month’s Republican primary runoff. “He will be a great Senator for the people of Alabama. Coach Tommy Tuberville, a winner, has my Complete and Total Endorsement,” Trump wrote.

Sessions is seeking a return to the Senate seat he held safely for 20 years before stepping down to become Trump's first attorney general. Sessions resigned as attorney general after their relationship soured over his recusal in the investigation into Russian interference in the 2016 election. Sessions said he was legally required to step aside because he was involved with the campaign.

Trump’s late-night endorsement tweet — and one before it that appeared to mock Sessions for being forced into a runoff — put an end to any hopes by Sessions supporters that the president would keep quiet on the Alabama race.

“Certainly, those around him were hoping that Trump would stay silent. I think they were ultimately hoping he would endorse Sessions, but short of that they were hoping he would stay silent. This certainly makes it much more difficult for Camp Sessions,” said Angi Stalnaker, another Alabama-based political consultant who works in Republican politics.

The Tuberville campaign began promoting the tweet heavily. Sessions said while the president has the right to endorse anyone he chooses, he would take his case directly to Alabama voters.

“I am one of the architects of the Trump agenda — I've always supported it and always will. Nothing the President can do will deter me from supporting this agenda, because my principles, just like my faith, are fundamental to who I am and immovable," Sessions wrote in a Wednesday night tweet.

However, while a Trump endorsement has boosted candidates in Georgia and elsewhere, it has not always equated to victory— even in Trump-loving Alabama.

He endorsed the previous appointed incumbent, Sen. Luther Strange who — hampered by questions of his appointment by a scandal-damaged governor — lost the Republican primary to Roy Moore. He then endorsed Moore who lost to Democratic Sen. Doug Jones in 2017 after Moore was wounded by sexual misconduct allegations during the race.

“He’s O for two,” Stalnaker said.

Sessions has remained a Trump loyalist. His first campaign video after announcing noted that he did not write a tell-all book or criticize Trump, after leaving the administration.

“He is almost the campaign equivalent of standing up at a wedding and saying you are still in love with the bride. He is pining for the support,” Mowery said.

Sessions was the first U.S. senator to endorse Trump's 2016 campaign and the new administration championed immigration, trade and criminal justice policies Sessions had touted for years.

“The sad irony is that the guy who basically helped create Trump is now getting killed by him,” Mowery said.