Even so, conservatives doubted his loyalty. In late October 2012, Hurricane Sandy had just devastated the Jersey Shore, and President Barack Obama went to survey the damage. Governor and president met on the tarmac at the Atlantic City International Airport. The two men shared a brief, friendly greeting but in conservative lore, it was framed as a protracted embrace — a betrayal of his party, then locked in a fierce presidential election to oust Mr. Obama.

As the G.O.P. embarked on its post-2012 “autopsy,” Mr. Christie made his own bipartisan pivot, which culminated in a traffic jam on the George Washington Bridge (i.e., Bridgegate). He was ruthless in his criticisms of Mr. Trump in 2015, only to remake himself as a Trump supporter early the following year, during a crucial time in the G.O.P. race. As late as November 2021, almost a year after the Capitol riot, Mr. Christie was still presenting himself as personally close with Trump. “We have been friends for twenty years and still are friends,” he wrote in “Republican Rescue,” the book he published that fall. In another passage, he wrote, “We’ve had great times together, and I have agreed with so many of the policies he pursued and achieved.”

That record of praise for Mr. Trump makes the broadsides Mr. Christie is now delivering on the campaign trail and in the debates (e.g., “Donald Duck”) all the more difficult to believe.

To his supporters, Mr. Trump’s contempt for the Republican establishment is a sign that he is unbought and unbossed. Mr. Christie’s record makes it difficult to convince voters that he is a maverick of similar issue. As one participant in a recent Republican focus group put it, “He has a lot of things from his past.” Even if he can somehow win the New Hampshire primary, those intrinsic flaws will remain.

Mr. Christie’s misfortune may have been to come of age in an unsustainably brutal political culture that rewards venality and dishonesty. Many of the American heroes he cited in his presidential announcement at Saint Anselm — F.D.R., J.F.K., Reagan — were far from perfect. But they felt the demand, the requirement even, to live up to some ideal of public service. Once that ideal vanishes, commercialized and deconstructed into obsolescence, so does the demand. And then only vanity remains.