The truth is that the road to Trumpism began long ago, when movement conservatives — ideological warriors of the right — took over the G.O.P. And it really was a complete takeover. Nobody seeking a career within the party dares to question any aspect of the dominating ideology, for fear of facing not just primary challenges but excommunication.

You can see the continuing power of the orthodoxy in the way all of the surviving contenders for the Republican nomination, Mr. Trump included, have dutifully proposed huge tax cuts for the wealthy, even though a large majority of voters, including many Republicans, want to see taxes on the rich increased instead.

But how does a party in thrall to a basically unpopular ideology — or at any rate an ideology voters would dislike if they knew more about it — win elections? Obfuscation helps. But demagogy and appeals to tribalism help more. Racial dog whistles and suggestions that Democrats are un-American if not active traitors aren’t things that happen now and then, they’re an integral part of Republican political strategy.

During the Obama years Republican leaders cranked the volume on that strategy up to 11 (although it was pretty bad during the Clinton years too.) Establishment Republicans generally avoided saying in so many words that the president was a Kenyan Islamic atheist socialist friend of terrorists — although as the quote from Mr. Rubio shows, they came pretty close — but they tacitly encouraged those who did, and accepted their endorsements. And now they’re paying the price.

For the underlying assumption behind the establishment strategy was that voters could be fooled again and again: persuaded to vote Republican out of rage against Those People, then ignored after the election while the party pursued its true, plutocrat-friendly priorities. Now comes Mr. Trump, turning the dog whistles into fully audible shouting, and telling the base that it can have the bait without the switch. And the establishment is being destroyed by the monster it created.