At times during tonight’s debate, Donald Trump seemed controlled, succinct, even prepared.

It didn’t matter. In an instant, he lost the debate and blew his chance of using it to turn around his sinking campaign.

That instant came when Trump refused to say he would respect the outcome of next month’s vote.

Barring some massive unforeseen news, that comment will dominate political conversation in the coming days. By next week, it will be all anyone remembers about tonight. And for good reason. A major party nominee suggesting he won’t concede defeat in a presidential election he has clearly lost was, until Trump came along, unthinkable. Had Al Gore taken that position in 2000, the United States might not be a functioning democracy today. If Trump’s position becomes the new normal--if future candidates refuse to respect the voters’ will--America may not remain one. Democracies require public legitimacy for their survival. When powerful actors withhold that legitimacy, the system crumbles.

The good news is that Trump’s answer will devastate him politically—perhaps even more than the groping scandals. It will devastate him because the minute the debate ends, journalists will begin asking every Republican they can find whether they agree that he doesn’t need to concede defeat. And many of those Republicans—including the ones on Trump’s own campaign—will feed him to the wolves.

Mike Pence, Trump’s own running mate, has already said he’ll accept the election outcome. Trump’s campaign manager, Kelly Anne Conway, has said something similar. The Republican National Committee’s Sean Spicer has said the RNC will accept the results. So has Laura Ingraham. Spicer, Ingraham, Conway and Pence want a career in the GOP post-Trump. They have no choice.

The media largely structures its coverage around partisan disagreement. If a candidate’s own party won’t defend something he says, journalists treat that statement as illegitimate. Which means that Trump, by refusing to commit to respect the election outcome, has just given the media an excuse to savage him in the days to come.

For months now, Hillary Clinton has been arguing that Trump represents a threat to American democracy. Tonight he made her point more effectively than she could ever have dreamed. He’s handed the media and his fellow Republicans the rope with which to hang him. They’re going to do so with glee.