In J.D. Vance, Donald Trump Selects an Inheritor

For nearly nine years, Donald J. Trump has been the singular face of Republican politics and the undisputed leader of the Make America Great Again movement. On Monday, the former president came as close as he may ever come to anointing a successor.

The choice of J.D. Vance as Mr. Trump’s running mate, a politician nearly 40 years his junior, immediately vaults the first-term senator to the forefront of a G.O.P. future that is not so far away.

If elected in November, Mr. Trump, 78, can serve only a single term — the 22nd Amendment states that no person shall be elected president more than twice — a rarity for a candidate naming a potential vice president. That short tenure has added extra urgency to the question of what comes next for Trumpism, a movement inextricably tethered to one man who has so thoroughly transformed the Republican Party.

Mr. Vance, 39, is the first millennial to make a major presidential ticket, a Marine veteran and a politician who has thoroughly remade himself as a full-throated MAGA enthusiast. In recent months, it was Mr. Vance’s aggressive defense of Trumpism and Mr. Trump, even on mainstream news outlets, that helped him stand out for the former president as a worthy inheritor.

“Trump is going to hold on to the MAGA baton for as long as he can,” said Chip Saltsman, a longtime Republican strategist. But Mr. Vance, he added, is “somebody that’s going to have an inside track, a head start on getting the MAGA baton in four years.”

The changing of the ideological guard was clearly, and at times uncomfortably, apparent on the convention floor on Monday. Mentions of Mr. Vance’s name earned roars of approval. The face of Senator Mitch McConnell, an avatar of the pre-Trump G.O.P., inspired boos when he appeared on the big screens above delegates.