As the world now knows, these feelings of powerlessness, resentment and grievance are widespread, and as a candidate Mr. Trump tapped into them perfectly. Many Republican voters have, at least for now, jettisoned traditional conservatism in favor of the Trump-Bannon brand of ethnonationalism. They have turned inward instead out outward, they have embraced white identity politics as a matter of course and they have developed a disdain for the hard, intricate work of governing.

But the reasons for the rise of Mr. Trump lie still deeper than that. There is a nihilistic strain coursing through the veins of a significant number of people on the American right. They delight in Mr. Trump’s effort to annihilate truth and peddle conspiracy theories, and they draw energy and purpose from the unsettling effect he has on the nation as a whole. For them, Mr. Trump is a “fighter,” and politics needs to be weaponized in order to be enjoyed. They see politics as World Wrestling Entertainment, and Mr. Trump as the best wrestler in the ring.

As a result, they are bending their will to his ways, seeing the world as he does. Take just one example that continues to startle: Russia. It wasn’t long ago that Republicans were nearly unanimous in their critical outlook on Russia. But today, because of Mr. Trump’s repeated praise for President Vladimir Putin, Republican attitudes toward Russia are far more favorable. A Pew Research Center poll found that the share of Republicans expressing confidence in Mr. Putin has doubled in just two years (from 17 to 34 percent).

Republicans, then, are faced with an existential question. Will Mr. Trump and his most ardent supporters succeed in their effort to reconceive the party? Can they be stopped? Certainly, if they don’t encounter more spirited resistance than they have so far, they may well pull it off.

Let me explain what I mean. Some so-called establishment Republicans, alarmed by the rise of the ethnonationalist wing of the party, comfort themselves with the belief that this movement can be domesticated, absorbed into the traditional coalition with its sharp edges sanded off. According to this narrative, the Republican Party will weather this storm and emerge in a modified but recognizable form. There are bound to be tensions, but civil war can be averted.