For about two weeks, until Donald Trump swept another round of elections on Tuesday, Republicans had settled on a line of attack that finally threatened to do him lasting damage. Rather than portray him as a bully or a clown or (disingenuously) as a liberal, they called him a con artist and a manipulator. In a subtle acquiescence to his campaign of demagoguery, they warned Republican voters not to be taken in by his appeals to their fears and biases—not because their fears and biases are unfounded, but because, as a con artist, he couldn’t be counted on to actually address them. 

Then, just as quickly, that line of attack disappeared—and was nowhere to be heard at Thursday night’s debate in Miami.  

The Republican presidential primary campaign has been bedeviled all along by a collective-action problem that has manifested in various ways. It appeared first as reluctance among frontrunners to attack Donald Trump at all, which created an incentive for other insurgent candidates like Ted Cruz to champion his message. That unorchestrated approach lead other well-positioned candidates to attack one another, and ultimately drove otherwise viable candidates (Scott Walker, Rick Perry) from the campaign earlier than expected. 

As the race narrowed, pretenders to the nomination stepped forward, one at a time, to mount anti-Trump attacks on behalf of the entire field. Each one was damaged—most famously Jeb Bush, who dropped out after losing badly in South Carolina. Ted Cruz, Marco Rubio, and John Kasich survived this process, all hoping to emerge as Trump’s sole competitor for the nomination. But none of them has been able to force the others out. Now, with Trump poised to win the nomination, his competitors are again unwilling to attack Trump in any damaging way.

On Thursday, just days before Trump could effectively end the primary by taking the winner-take-all contests in Ohio and Florida, the collective-action problem manifested as sheer bafflement. For two hours, Trump, who refrained for the first time ever from taunting his rivals, drew almost no sustained criticism.

Acting in a subdued manner may be the greatest con of Trump’s campaign. Trump has essentially admitted it’s an affected disposition—he likes to boast about how presidential he’s capable of behaving when he wants to. And yet suddenly, at the most critical juncture of the race, none of the rivals, who one week ago were happy to call Trump a con man, were willing to implore GOP primary voters to reject him.

Whether this reflects resignation, or a fear of looking ridiculous at the crucial last minute (as Marco Rubio did last month when he suggested Trump had small genitals), it allows Trump to enter the next round of primaries without a cloud of debate-stage negativity hanging over his head.

Should Trump win the nomination, largely as a result of this collective-action problem, he will enter the general-election campaign crippled. He is fatally unpopular with female voters and minorities, and not nearly popular enough with white men to close the gap.

Many liberals fear the prospect of Trump’s nomination, because they worry his feigned populism will expand the electorate in ways that might allow him to win. They assume, with good reason, that the Republican Party (or large segments of it) will reconcile itself to his nomination, and that by closing ranks, the people who now say #NeverTrump will help propel him to victory.

It is far, far likelier that Trump will lose the general election by a larger margin than Democrats deserve. When that happens, Republicans will relearn how to call Trump a con man. To anyone who will listen, they will disclaim him as a fluke—a skilled entertainer who ran an infomercial-like campaign and swindled Republicans into supporting him. They will see it as the path of least resistance, the only argument they can make to avoid reckoning with the fact that the Trump phenomenon is actually the product of years of Republican maximalism and apocalyptic rhetoric.

The challenge for everyone else will be to remind them of nights like tonight—when, faced with the prospect of a bigoted demagogue taking over their party, they said nothing.

Want to learn more about the 2016 primaries? Take a listen to an episode of Primary Concerns, a podcast on politics and the primaries, hosted by Brian Beutler: