LONDONDERRY, N.H. — Chris Christie’s name has tumbled off the list of top-tier presidential candidates. He is sagging in the polls. And in the kind of indignity that creeps up on him with agonizing regularity, a stranger here wisecracked Wednesday morning that he and his wife had been stuck in the George Washington Bridge traffic jam engineered by the governor’s allies — on their wedding anniversary, no less.

“Really?” Mr. Christie asked, seeming legitimately surprised when he met the man at a Manchester diner. “How’d it go? Not well, right?”

As his rivals declare their candidacies for the White House with flashy events from Florida to Virginia, Mr. Christie is pursuing a humbling and painful path of rehabilitation: huddling with aides to plot a comeback, churning through a thick reading list to burnish his shaky command of foreign policy and showing up at intimate venues to convey the message that he is still alive.

With the possibility of imminent and embarrassing indictments hanging over his administration, Mr. Christie is turning to a political format, the town hall meeting, that has propelled him through rough patches in the past, and to a state, New Hampshire, whose forgiving and independent-minded voters are known for reviving once-moribund presidential campaigns.