Former Attorney General Jeff Sessions announced a bid Thursday to reclaim his old Senate seat in Alabama, setting up a potentially bruising Republican primary in one of the marquee 2020 Senate races.

A year to the day since President Donald Trump forced him out of the Justice Department, Sessions launched his campaign to win back a position he held for about two decades. The 72-year-old, who was the first senator to endorse Trump's presidential candidacy in 2016, will now have to navigate a pro-Trump state as a target of the president's ire.

In a statement which was posted on his campaign website, Sessions praised Trump despite the president saying that nominating him as attorney general had been the "biggest mistake" of his presidency.

"When President Trump took on Washington, only one Senator out of a hundred had the courage to stand with him: me. I was the first to support President Trump," Sessions said in his statement. "I was his strongest advocate. I still am. We must make America great again."

He added: "Our freedoms have never been under attack like they are today. We have major party candidates for President campaigning on socialism, confiscating firearms, and closing down churches they disagree with. I've battled these forces my entire life, and I'm not about to surrender now. Let's go!"

Sessions also tweeted out a video of the announcement, his first tweet since Nov. 4, 2014.

Sessions hopes to challenge Sen. Doug Jones, a Democrat who won the 2017 special election to finish Sessions' term when he left to become attorney general. He will have to fight his way through a jammed primary filled with GOP candidates who have already tried to paint him as disloyal to Trump in a state where the president is overwhelmingly popular.

Even so, the 2017 race showed Trump's support can only go so far in Alabama. The president endorsed Sen. Luther Strange, the Republican chosen to temporarily fill Sessions' seat, only to see him lose the the GOP nomination to former state Supreme Court Chief Justice Roy Moore. He eventually lost to Jones amid accusations that he sexually abused teenagers decades ago while he was in his 30s.

Republicans covet the Alabama Senate seat, the GOP's best chance to flip a Democratic-held state in 2020. Republicans aim to hold their 53-47 majority in the chamber as they defend 23 seats next year.

Even if Trump does not back him, Sessions looks like he will get the support of at least one powerful Alabama Republican. Sen. Richard Shelby, R-Ala., said Thursday he would "absolutely" endorse Sessions, according to CNN.

Sessions also has the strong name recognition that comes with representing Alabama in the Senate for more than three terms.

In the Republican primary, the ex-senator will face candidates including U.S. Rep. Bradley Byrne, former college football coach Tommy Tuberville, Alabama Secretary of State John Merrill and Moore. In statements Wednesday night, both Byrne and Tuberville criticized Sessions for his supposed disloyalty to Trump.

The president repeatedly thrashed his ex-attorney general over his decision to recuse himself from the investigation into Russian efforts to interfere in the 2016 election, due to his ties to the Trump campaign. Sessions' move led in part to the appointment of former FBI Director Robert Mueller to oversee the probe as special counsel.

"The Russian Witch Hunt Hoax continues, all because Jeff Sessions didn't tell me he was going to recuse himself...I would have quickly picked someone else," Trump wrote in a June 2018 tweet.

In August 2018, he wrote: "If we had a real Attorney General, this Witch Hunt would never have been started!"

Various reports during Sessions' tenure at the Justice Department showed a president who openly mocked his attorney general. The president told aides he could not stand Sessions' southern accent, and said the former senator "talks like he has marbles in his mouth," according to a Politico report last year.

At some points, Trump reportedly called Sessions "Mr. Magoo" — a nickname based on a cartoon character The Washington Post called "elderly, myopic and bumbling." Trump also called his ex-attorney general a "dumb southerner," according to journalist Bob Woodward's book "Fear."

Trump has denied throwing many of those epithets at Sessions.

Aside from Trump's distaste for him, Sessions faces other potential challenges in the race. He enters a Republican primary that has already started to take shape in his absence.

He would have to scramble to catch up to Jones' fundraising, after the senator raised $2 million in the third quarter and ended the period with about $5 million on hand.

Byrne, who took in about $381,000 in the third quarter, ended September with about $2.5 million in the bank. Tuberville raised about $373,000, ending the third quarter with nearly $1.5 million on hand.