In his first televised interview since leaving office, Mr. Sessions told Fox News’ Tucker Carlson on Thursday that he had no regrets about the recusal. “I did the thing I had to do under the rules of the Department of Justice,” he said, acknowledging, “I know how painful this was for the president.” He added that he has not yet spoken with Mr. Trump about his Senate campaign but hopes to.

Because Mr. Trump has an almost imperial hold on the Republican Party, Mr. Trump’s dislike could make for a rough road ahead for Mr. Sessions. Republicans who find themselves in Mr. Trump’s political cross hairs rarely fare well with their party’s voters. And the president has sent word to the former attorney general through allies that he would publicly attack him if he went ahead with the campaign.

But Mr. Sessions, 72, has been an admired figure in Alabama Republican politics for four decades and, by many accounts, remains popular there despite the withering scorn Mr. Trump has leveled at him. Among other insults, Mr. Trump has accused Mr. Sessions of betrayal and of being a “total joke” of a leader at the Justice Department. More recently, the president has referred to him as a “jerk” in private conversations.

On Friday, according to a pool report, Mr. Trump was asked if he would campaign against Mr. Sessions. “I won’t. I’ll see how it all goes, ” Mr. Trump said on his way to board a flight to Atlanta. “We’ll see what happens, he’s got tough competition.”