Hillary Clinton gave the speech about Donald Trump that, with a few changes, House Speaker Paul D. Ryan (R-Wis.) could have given. And he should have.

With her address, she assumed the role of the Democratic presidential nominee, even if the delegate numbers hadn’t quite ratified that yet.

Instead of sticking to his vaunted principles, Ryan forged a link between the Republican Party and Donald Trump that may endure in public consciousness long after this campaign is over.

There will be some brave dissenters, especially among Republicans and conservatives who do not hold elected office (and former presidents named Bush).

But party leaders have decided that Trump’s nativism and racism, his utter disrespect for the judicial system, his soft spot for foreign dictators and his latent authoritarianism matter far less to them than holding on to power in Congress. It will be up to the voters to decide how big a price Ryan, Mitch McConnell & Co. should pay for this.

Remember the date: Thursday, June 2, 2016. It will be seen as the day when the choice facing us in this election was finally clarified.

Clinton’s speech did nothing more (or less) than show how ridiculous and self-destructive it would be for a democratic superpower to elect Trump as president. Not only did the emperor emerge with no clothes. The very idea of him as a head of state of any kind became laughable.

There were no punches pulled as Clinton came up with one sound bite after another to capture who Trump is and what he does — “dangerously incoherent,” “bizarre rants,” “personal feuds,” “outright lies.”

More tellingly, she shredded his standing by doing the most effective kind of negative campaigning where Trump is concerned: She quoted or accurately paraphrased him, over and over. Two of the best lines: “He says he has foreign policy experience because he ran the Miss Universe Pageant in Russia,” and, “You know, there’s no risk of people losing their lives if you blow up a golf course deal.”

And also this: “I will leave it to the psychiatrists to explain his affection for tyrants.”

By going back several times to Trump’s apparent love affair with dictators, Clinton sent a larger message. Alongside her vast inventory of absurd Trumpisms, Clinton offered a contrast between her view of the United States and Trump’s. She is an optimist who believes in our country’s present, its future and its role in the world. He is a pessimist who seems to think that only strongman, Putin-inspired leadership can save us from the abyss.

Here is the key sentiment:

“He believes America is weak, an embarrassment. He called our military a disaster. He said we are — and I quote — ‘a Third World country.’ . . . Those are the words, my friends, of someone who doesn’t understand America or the world. . . . If you really believe America is weak, with our military, our values, our capabilities that no other country comes close to matching, then you don’t know America. And you certainly don’t deserve to lead it.”

This passage explains why none of Trump’s Republican foes could give Clinton’s speech — positively Reaganesque in its patriotic embrace of American exceptionalism — at a point during the primaries when Trump might have been stopped.

During President Obama’s tenure, Republicans, Ryan included, became deeply committed to describing a country in ruinous decline. They insisted that we had lost our core values; that Obama had radically undermined an economy that, in fact, he had helped rebuild; and that our nation was under the control of forces so alien that we needed to “take it back.”

Trump, coarsely but unsparingly, has given voice to the extreme hopelessness that has gripped such a broad swath of the Republican electorate — egged on in its anxieties by its more conventional leaders.

Thus Ryan’s appalling but entirely predictable capitulation. His sunny personality conveys optimism. But the House speaker knows the band he leads in Congress includes many who have been selling Trumpian despair out of conviction and scores of others who pretend to an unrelenting gloom because this is the attitude their primary voters demand of them.

And so Ryan and his colleagues will now be stuck defending an indefensible man even as Hillary Clinton occupies Lincoln’s high ground in proclaiming our country as “the last best hope of Earth.” There is, however, this: Many who say they support Trump will be praying quietly and fervently for Clinton to prevail. Ryan may be among them.