But Mr. Graham’s reaffirmed devotion has come to represent something more remarkable: his party’s headlong march into the far reaches of Trumpism. That the senator is making regular Palm Beach pilgrimages as supplicant to an exiled former president who inspired the Capitol attack and continues to undermine democratic norms underscores how fully his party has departed from the traditional conservative ideologies of politicians like Mitt Romney, Liz Cheney and Mr. Graham’s close friend John McCain…

He alone can fix the former president, he believes, and make him a unifying figure for Republicans to take back both houses of Congress next year and beyond. To that end, he says, he is determined to steer Mr. Trump away from a dangerous obsession with 2020…

Many of Mr. Graham’s old friends on both sides of the aisle — and he still does not lack for them — grudgingly accepted as political exigency his original turn to Mr. Trump. His deviations from conservative orthodoxy, they understood, had left him precariously mistrusted back home. Now, though, they fear he has reached a point of no return.

“Trump is terrible for the country, he’s terrible for the Republican Party and, as far as I’m concerned, he’s terrible for Lindsey,” said Mark Salter, a close McCain friend who was the ghostwriter for Mr. Graham’s autobiography.