But for all the attention paid to what Trump represents in American politics, the most salient feature of his ascent within the Republican Party might be what he doesn’t represent. When Ronald Reagan overthrew the old order of the Republican Party in the 1980 election, he did so as the figurehead of a conservative movement that had been gestating since the 1950s, with an intellectual framework that William F. Buckley Jr. had been articulating for a quarter-century, with a policy blueprint provided by the Heritage Foundation and with a campaign apparatus that quickly pivoted to the task of converting the new constituencies he’d brought into the party to a base durable enough to build on. The total merger of his movement with his party didn’t happen immediately, but the key elements of it were in place by the end of his first term, and there was not much ambiguity about what the G.O.P., if it was transforming, was transforming into.

Trump’s takeover, by contrast, has been as one-dimensional as it has been total. In the space of one term, the president has co-opted virtually every power center in the Republican Party, from its congressional caucuses to its state parties, its think tanks to its political action committees. But though he has disassembled much of the old order, he has built very little in its place. “You end up with this weird paradox where he stands to haunt the G.O.P. for many years to come, but on the substance it’s like he was never even there,” said Liam Donovan, a Republican strategist…

But Trump’s influence is also reflected, in a more pedestrian but equally revealing way, in the ease with which George Kruse and others like him have transposed Trumplike signifiers onto otherwise utterly conventional suburban Republican platforms. Republican voters are essentially the same people who voted Republican before Trump; the party’s politicians are still mostly the same people, hiring mostly the same strategists. But their relationships to the party now flow through a single man, one who has never offered a clear vision for his political program beyond his immediate aggrandizement. Whether Trump wins or loses in November, no one else in the party’s official ranks seems to have one, either.