For one thing, Republican voters are angrier than they used to be, as I describe in a companion article. They are angry about the great wage slowdown that has bedeviled the American economy for more than 15 years. And many are unhappy about a set of cultural changes that have occurred over the same period.

In this environment, party elites don’t hold the sway they once did. They seem to realize it, too, with strikingly few elected officials offering endorsements so far. Mr. Cruz has sometimes reveled in party leaders’ disdain for him — a stance that would have been fatal not so long ago.

Perhaps just as important, he has been able to raise large sums of money despite his hostile relationship with much of the party. “He has succeeded in building a robust campaign organization,” my colleague Nate Cohn has written, “buoyed by fund-raising tallies of the sort we generally haven’t seen from anti-establishment, conservative candidates.”

One factor is that some Republican elites have become radicalized in similar ways to the Republican base. Another is that elites who disagree with the party establishment can probably have a greater influence than in the past. The rise of inequality has created more deep-pocketed potential conservative donors, while the loosening of campaign-finance rules has made it easier for those donors to give large sums.