(CNN) Former Attorney General Jeff Sessions announced a campaign for his old Alabama Senate seat on Thursday, betting that President Donald Trump will not be able to break the bond that Sessions built with the state's voters over two decades.

The announcement came a year after Trump fired Sessions from his dream job, and their relationship will now be a determining factor in the race.

Sessions addressed it head-on in a video launching his campaign, saying Trump has "my strong support." He then expressed his loyalty to the President by noting that he did not attack Trump despite his former boss' withering, public criticism.

"When I left President Trump's Cabinet, did I write a tell-all book," asked Sessions. "No. Did I go on CNN and attack the President? Nope. Have I said a cross word about our President? Not one time."

Sessions said that would've been "dishonorable," adding he "was there to serve his agenda, not mine."

While Sessions has been beloved in Alabama — his last Senate campaign in 2014 was unopposed — Trump commands higher approval ratings there than just about any other state. And the President spent months criticizing his first attorney general, personal attacks that could very well sway the party's primary on March 3.

But Sessions did not leave on good terms. Trump never forgave the Alabamian's decision to recused himself from the Justice Department's investigation of Russian interference in the 2016 election, citing his role on behalf of the Trump campaign.

Sessions' argument did not sway the President, who repeatedly criticized him for the probe, which former special counsel Robert Mueller took over after Trump fired FBI director James Comey. The President's condemnation rose to the point that for months Sessions carried a resignation letter with him in his pocket when he went to the White House, according to the Mueller report.

In November 2018, Trump fired Sessions and wished him well. But the attacks continued. A month after the firing, he tweeted, "Jeff Sessions should be ashamed of himself for allowing this total HOAX to get started in the first place!"

When asked on the White House lawn by CNN on Friday if he would endorse Sessions, Trump said, "I saw he said very nice things about me last night, but we'll have to see."

Other Republican candidates are already pitching themselves as better stewards of Trump's political brand. Former Auburn football coach Tommy Tuberville, US Rep. Bradley Byrne, Secretary of State John Merrill, former Chief Justice Roy Moore, State Rep. Arnold Mooney and businessman Stanley Adair are all running for the party's nomination.

Tuberville took a shot at Sessions on Wednesday, calling him a has-been who lost his opportunity to defend Trump.

"As Attorney General, Jeff Sessions had his chance to have President Trump's back and take on the establishment politicians and he failed," he said. "I will bring a new voice for Alabama to the Senate and I will always have President Trump's back."

But other Alabama Republicans said Sessions still holds political power in the state. GOP Sen. Richard Shelby of Alabama said that he would "absolutely" endorse Sessions, calling him a "formidable candidate."

"Jeff Sessions is a friend," said Shelby. "I worked with him every day up here for 20 years. He's a man of integrity.

Merrill told CNN that if Sessions got in the race, he'd be the frontrunner due to long experience representing Alabama in the Senate.

"No doubt about it," said Merrill. "He held the seat for 20 years."

The race is Republicans' best opportunity to add to their 53-person majority in the Senate. In 2017, Democrat Doug Jones, a US attorney, beat former Chief Justice Roy Moore, who faced allegations that he sexual assaulted teenage girls in his 30s -- charges Moore vehemently denied. Moore also was twice removed from the bench, for refusing a federal order to remove a Ten Commandment monument from the Alabama Supreme Court building and for ordering judges to not heed the Supreme Court's ruling on same-sex marriage.

While Moore is running again for Senate, many Republican strategists hope the party will nominate another candidate. The Senate Republican campaign arm has taken an-anyone-but-Roy-Moore approach.

"I'm not going to get involved in a primary, other than to say that I certainly don't want to see Roy Moore be the candidate," said Sen. Susan Collins, Republican of Maine, who is close enough to Sessions that she introduced him before his 2017 nomination hearing to lead the Department of Justice.

Sen. John Cornyn, Republican of Texas, said he talked to Sessions in person a couple days ago about his hope his former colleague and the President can repair their relationship.

"I told him I hope he and the President can work out their differences, because I think if not it's going to be a pretty miserable experience," said Cornyn. "I told him what he already knew."

Some top Republican officials are expressing their exasperation at Sessions over his decision to jump into the Alabama Senate race, fearing that internal party dispute could help reelect Jones. The Democrat has over $5 million on hand, the most of any candidate in the Senate race, according to the latest filings. Byrne has over $2.5 million, Sessions has over $2.4 million and Tuberville has over $1.4 million.

At a breakfast meeting on Thursday with about 50 lobbyists and others, officials from the National Republican Senatorial Committee openly voiced their concern about Sessions, according to two people in the room. The frustration was not rooted in dislike for the longtime senator, but rather the uncertainty over Trump's reaction to his former attorney general.

Sessions has not returned calls from the National Republican Senatorial Committee, two officials tell CNN, and is keeping counsel with a tight group of longtime advisers and friends.

"There is no one the President hates more and if he's the nominee and Trump continues to dump on him, Jones could be reelected," one Republican official told the crowd.

Sessions' announcement came one day before Alabama's filing deadline — and two days before Trump heads to Tuscaloosa for the University of Alabama-Louisiana State University football game.

Jones told CNN that he'll go to the game with West Virginia Sen. Joe Manchin, a Democrat and childhood friend of Alabama coach Nick Saban.

"It's going to be bedlam," Jones said.

This story has been updated with additional developments Friday.