Former US Attorney General Jeff Sessions has announced he is entering the Republican Party race to reclaim his former Senate seat in Alabama.
President Donald Trump fired his top law official last year after a protracted feud over the inquiry into 2016 election meddling, which Mr Sessions declined to oversee.
Mr Sessions, 72, held his Senate seat for two decades before serving as AG.
Mr Trump is expected to campaign against him.
In a statement announcing his run, Mr Sessions reiterated his support for the president despite their public "ups and downs".
"When I left President Trump's cabinet, did I write a tell-all book? No. Did I go on CNN and attack the president? No. Have I said a cross word about President Trump? No," a press release on his website said.
"And I'll tell you why: first, that would be dishonourable. I was there to serve his agenda, not mine. Second, the president is doing a great job for America and Alabama, and he has my strong support."
Mr Sessions also described himself in the statement as still being Mr Trump's "strongest advocate", in spite of being publicly ridiculed by the president.
The former senator is entering an already crowded race to seek the state's Republican nomination for the 2020 general election.
Among those who have announced their intention to run is former Chief Justice Roy Moore, 72, who lost the special election for Mr Sessions' seat in December 2017.
Mr Moore had been expected to win but his campaign was dogged by allegations of sexual misconduct with teenage girls.
He eventually lost out to Doug Jones, who became the first Democrat to win a US Senate seat in the deeply conservative state for 25 years.
An attack advert released hours after Mr Sessions launched his campaign told Alabama voters to "say no to traitor Jeff".
The video, funded by supporters of Tommy Tuberville, US football coach also running for the Senate seat, showed a speech by Mr Trump saying: "He's bad, he's a bad, bad guy".
Asked about Mr Sessions on Friday, Mr Trump told reporters: "I heard he said very nice things about me last night. I have to see. I haven't made a determination."
"You have some good people in Alabama," he said referring to other candidates. "We'll see what happens."
Mr Trump said he would not campaign against Mr Sessions.
Who is Jeff Sessions?
Mr Sessions is a lifelong conservative who worked as a lawyer and served in the US Army reserves before entering the political stage.
He became attorney general in Alabama - his home state - in 1994 and joined the Senate two years later.
He was also the first US senator to endorse Mr Trump during the 2016 presidential campaign.
During his time in Congress, Mr Sessions was an outspoken opponent of liberalising drug laws, gay marriage and immigration.
Despite remaining deeply popular in Alabama, he resigned from his post in the Senate in 2017 to become Mr Trump's first attorney general.
In March 2017, Mr Sessions recused himself from overseeing the Department of Justice's independent probe into Russian interference during the 2016 presidential election after it emerged he had met Russia's ambassador during the campaign.
The decision was criticised by Mr Trump, who blamed it for the appointment of Robert Mueller as special counsel by Assistant Attorney General Rod Rosenstein.
Mr Sessions was the butt of many presidential barbs - in August 2018 Mr Trump tweeted that his attorney general was "scared stiff and missing in action".
Mr Sessions was forced to resign less than three months later. A letter confirming the move made clear that the decision to go was not his own.