In a clip from a campaign ad, Sessions noted he never went on television to criticize Trump, nor did he "write a tell-all book".
In March 2017, Mr Sessions recused himself from overseeing the Department of Justice's independent probe into Russian interference in the 2016 presidential election.
By the time Sessions announced his run Thursday, multiple negative ads disparaging the former senator were online.
"When President Trump took on Washington, only one senator out of a hundred had the courage to stand with him: me", he says. Though Sessions's senate bid had been expected for weeks, its format was not: An awkward video for an executive audience of one, all but begging for his squiggly endorsement. Alabama is a heavily pro-Trump state, and so far the candidates appear to be competing over who is the most devoted to Trump. "No", Sessions said in his announcement statement.
"As everyone knows, President Trump and I have had our ups and downs".
"Have I said a cross word about our president?" Not one time and I'll tell you why. I was his strongest advocate. But here's the important part: "the President is doing great work for America", Sessions said in his campaign announcement.
And while politicians, operatives and analysts expect Sessions to become an immediate frontrunner for the GOP nomination, the big unknown is how Trump and his Alabama supporters will react. Richard Shelby earlier said he would endorse the former attorney general and believes he can win. We have major party candidates for president campaigning on socialism, confiscating firearms, and closing down churches they disagree with.
Sessions joins an already crowded field including Rep. Bradley Byrne, former Auburn University football coach Tommy Tuberville, Alabama Secretary of State John Merrill, state Rep. Arnold Mooney and Roy Moore, who lost the special election to replace Sessions to Democrat Doug Jones in 2017.
But Sessions did not leave on good terms. Setting aside the fact that Sessions' entry makes him the fifth candidate now running in an already crowded Alabama Senate Republican primary, Trump has more personal reasons for opposing Sessions.