Donald Trump is a moral monster. He wants to deport America’s 11 million unauthorized immigrants and build a wall on the Mexican border. He wants to kill the children of suspected terrorists and bring torture back to American intelligence gathering. He wants to ban Muslims (including citizens) from entering the United States, and he openly courts white supremacists for support.

And yet, he is leading the Republican race for president, with more votes and delegates than anyone else in the race.

For Republican elites, this fact is intolerable, which is why Mitt Romney—former Massachusetts governor, two-time presidential candidate, and one-time nominee—stepped to the plate on Thursday to oppose Trump’s march to the nomination with a speech at the University of Utah in Salt Lake City. His case was simple: “[I]f we Republicans choose Donald Trump as our nominee, the prospects for a safe and prosperous future are greatly diminished.”

To that point, Romney attacked Trump on all fronts. He blasted him on domestic policy. “His proposed 35 percent tarifflike penalties would instigate a trade war that would raise prices for consumers, kill export jobs, and lead entrepreneurs and businesses to flee America,” Romney said. “His tax plan, in combination with his refusal to reform entitlements and to honestly address spending would balloon the deficit and the national debt.”

Romney then hit him on foreign policy. “Trump’s bombast is already alarming our allies and fueling the enmity of our enemies. Insulting all Muslims will keep many of them from fully engaging with us in the urgent fight against ISIS,” he said. He made real and effective digs at Trump’s business acumen—“His bankruptcies have crushed small businesses and the men and women who worked for them”—and questioned Trump’s intelligence and honesty, aiming straight at Trump’s appeal. “Dishonesty is Trump’s hallmark,” said Romney. “His imagination must not be married to real power.”

Romney was strong and confident. He was detailed and specific. But he wasn’t effective. For all of his vehemence and disgust, Romney fell short with his saturation attack on Trump, for all the reasons that most GOP attacks have missed the mark.

To start, there’s no self-awareness. Romney didn’t say a word about his aggressive play for Trump’s endorsement in the 2012 presidential election. You can watch the press conference, where an effusive Romney hailed Trump as a figure par excellence: “There are some things that you just can’t imagine happening in your life. This is one of them. Being in Donald Trump’s magnificent hotel and having his endorsement is a delight. I am so honored and pleased to have his endorsement.”

This wasn’t a throwaway moment in Romney’s campaign. By that point, Trump was known for his racist “birtherism” and careless demagoguery. Romney chose to ignore this to win modest support from the GOP base. And by chasing Trump, Romney helped legitimize him as a figure in the Republican Party. To have any credibility in his present crusade against Trump, Romney needed to apologize. He needed to own his mistake and make that awareness a departure point for his case against “the Donald”—a warning, of sorts, from someone who was taken in by Trump and his charms.

Romney didn’t do this. Instead, well after his speech, he sent a tweet. “If Trump had said 4 years ago the things he says today about the KKK, Muslims, Mexicans, disabled, I would NOT have accepted his endorsement,” said Romney, ignoring Trump’s birtherism.

But then, Romney doesn’t seem to fully understand Trump’s appeal to Republican voters. Racism is one part of it. The other is deep economic insecurity, fueled by years of declining wages and supercharged by the Great Recession. Which is why Romney’s attack on economics—Trump refuses to “reform entitlements”—is a misfire. Far from undermining Trump, it emphasizes his appeal: that he’ll protect retirement programs and bring security to middle-class (white) Americans. Trump’s voters don’t want to fight for survival in the free market. They want protection. They want to be safe.

By themselves, these mistakes weren’t fatal. The fact that a former GOP presidential nominee is speaking against a prospective one is almost enough—this is the dynamic that presages a failed campaign in November—and Romney deserves credit for it. But he undermines this by making a moral case against Trump that’s still subordinate to other concerns. Rather than ask Republicans to reject Trump because he’s immoral, Romney (and other Republicans) harp on one particular point: Trump will lose the election. “A person so untrustworthy and dishonest as Hillary Clinton must not become president,” said Romney “But a Trump nomination enables her victory.”

This is the unshielded exhaust pipe of the elite Republican argument against Trump—the fatal flaw that undermines the entire structure. First, there’s the fact that if the core objection is partisan—to stop Hillary Clinton—then Romney is a terrible messenger. As the GOP nominee in 2012, he didn’t just lose to Barack Obama, he lost badly, in an election that the party sold as a cakewalk, where Americans would welcome Republicans as liberators from a failed administration. They were wrong. And now, Republican voters believe Trump is their best chance to beat Democrats in the fall. After all, he’s a fighter. Just look at his response to Romney’s speech, mocking Romney for seeking his support: “I could have said, ‘Mitt, drop to your knees.’ He would have dropped to his knees.”

Instead of making the morality of the case subordinate to the electoral calculation, Romney and other anti-Trump Republicans need to make the election subordinate to morality. If Trump is more than a threat to the GOP—if he, as Romney says would lead this nation “into the abyss”—then Republicans need to say they’re willing to lose the election, and hand the Oval Office to Hillary Clinton, if it means stopping Trump. They don’t have to endorse Clinton, but they need to say that, if Trump is the nominee, they will not support him. It’s the only step that might shatter Trump’s coalition, or—in the fall—keep party unity from giving Trump a fighting chance, ending his viability as a general election candidate.

It is a terrible choice to have to make for the party men and women of the GOP. But if Romney is right—if Trump is a threat to American democracy itself—then it’s the only weapon they have left.

Read more Slate coverage of the 2016 presidential election.