Hillary Clinton celebrates after accepting the Democratic presidential nomination at the Democratic National Convention in Philadelphia last month. (Michael Robinson Chavez/The Washington Post)

Donald Trump was no more knowledgeable, stable or coherent during the primary than he is now, and yet Republicans failed to exploit opportunities Hillary Clinton is now capitalizing on, to the chagrin of Republicans who fear that a landslide is in the offing.

Multiple GOP presidential campaigns in the primary refused take on Trump for suggesting that he would order the military to commit war crimes. It’ll just make us look weak if we raise it, they told me at the time. These were supposed to be the people who revere the rule of law and the military. Not so much in the heat of a primary fight, I guess.

It was the same on Trump’s immigration plan, including his Muslim ban and idiotic wall, which in some dark recess of his mind he imagined Mexico could be bullied into paying for. After Jeb Bush left the race, no Republican took these head-on, bothering to explain that they were counterproductive and that it would be contrary to our values for troops to root out suspected illegal immigrants, separate them from families and communities and deport able-bodied workers, who buy goods and contribute at minimum sales and Social Security taxes.

Republicans could and should have done this from the right. Only as he was exiting the race did Sen. Ted Cruz (R-Tex.) make the case on temperament, accusing him of pathological lying and amorality. They apparently lacked the nerved to mock Crazy Donald, or whatever name Democrats now have come up with to describe an unraveled, unhinged narcissist.

Unlike Republicans, Clinton, of all people, is attacking Trump from the right and making his character, temperament and, yes, sanity an issue.

On the war-crimes issue, she has repeatedly hit him for endangering our troops. It is part of her persuasive argument that he is unfit to be commander in chief. In early June in her hard-hitting foreign-policy speech, she went after Trump: “So it really matters that Donald Trump says things that go against our deepest-held values. It matters when he says he’ll order our military to murder the families of suspected terrorists.” At her convention she likewise declared, “We entrust our commander in chief to make the hardest decisions our nation faces. Decisions about war and peace. Life and death. A president should respect the men and women who risk their lives to serve our country — including the sons of Tim Kaine and Mike Pence, both Marines. Ask yourself: Does Donald Trump have the temperament to be commander in chief?”

On the Muslim ban, she has attacked Trump for failing to respect religious freedom and undermining our efforts to defeat the Islamic State. (“His proposal to ban 1.5 billion Muslims from even coming to our country doesn’t just violate the religious freedom our country was founded on. It’s also a huge propaganda victory for ISIS. And it alienates the very countries we need to actually help us in this fight.”) Now she is using his anti-Muslim bigotry to appeal to Mormons. In Utah. Yes, really. She writes in an op-ed for a local Utah paper:

Trump’s Muslim ban would undo centuries of American tradition and values. To this day, I wonder if he even understands the implications of his proposal. This policy would literally undo what made America great in the first place.

But you don’t have to take it from me. Listen to Mitt Romney, who said Trump “fired before aiming” when he decided a blanket religious ban was a solution to the threat of terrorism.

Listen to former Sen. Larry Pressler, who said Trump’s plan reminded him of when Missouri Gov. Lilburn Boggs singled out Mormons in his infamous extermination order of 1838.

Or listen to your governor, who saw Trump’s statement as a reminder of President Rutherford B. Hayes’ attempt to limit Mormon immigration to America in 1879.

Instead of giving into demagoguery, Gov. Gary Herbert is setting a compassionate example and welcoming Syrian refugees fleeing religious persecution and terrorism. Once they’ve gone through a rigorous screening process, he is opening your state’s doors to some of the most vulnerable people in the world.

Republicans surely could have done all that around the country. The party should have done it as soon as it became obvious to the casual observer that Trump was thoroughly unfit. They did not, both because they were trying to placate the same intolerant mob that Trump was entreating and in part because they’ve become hypocritical advocates not of religious liberty but on behalf of evangelicals. They put out their own preposterous statements insisting that refugees (among the most thoroughly vetted newcomers) were stocked with terrorists who’d pour into the country without their draconian measures. They vied for the most anti-immigrant policy. They eschewed the traits Republicans normally are associated with — sobriety, humility, reason, prudence and faith-based morality.

If Clinton now sounds like a Republican (respect for the military, defense of the rule of law, respect for religious minorities), it’s because Republicans forfeited much of the center-right ground in a fruitless effort to out-crazy Trump. If Clinton is smart, she will keep at it, creating a vast center-left to center-right coalition. She did not so much steal the GOP’s issues and thoughtful voters; rather, the GOP gave up on both. Now, it’s too late to get them back.