There is no way to sugarcoat this: At Sunday night’s presidential debate, Donald Trump threatened to throw Hillary Clinton in jail if he wins the presidency. This — threatening to jail one’s political opponents — is how democratic norms die.

The exchange happened during a discussion of the controversy over Hillary Clinton’s private email server. Trump began by decrying Clinton’s conduct — which, according to the FBI, was quite bad but not illegal. He then proposed appointing a special prosecutor to investigate her, and warned Clinton that, if he were president now, “you’d be in jail”:

TRUMP: I'll tell you what. I didn't think I'd say this, and I'm going to say it, and hate to say it: If I win, I'm going to instruct the attorney general to get a special prosecutor to look into your situation because there's never been so many lies, so much deception … A very expensive process, so we're going to get a special prosecutor because people have been, their lives have been destroyed for doing one-fifth of what you've done. And it's a disgrace, and honestly, you ought to be ashamed. CLINTON: Let me just talk about emails, because everything he just said is absolutely false. But I'm not surprised … It's just awfully good that someone with the temperament of Donald Trump is not in charge of the law of our country. DT: Because you'd be in jail.

This is so far beyond normal that it’s hard to even know where to start.

In democracies, we respect people’s rights to disagree with each other. When one candidate wins a presidential election, the loser returns to private life or another government position. In some cases, former rivals become close friends. George H.W. Bush and Bill Clinton, who defeated Bush in the 1992 election, travel together and have spent decades jointly raising money to aid the victims of natural disasters.

They don’t get sent to jail, because we believe that political disagreement should be legal.

Donald Trump doesn’t seem to care about all that.

In his last line — “you’d be in jail” — he is outright saying that he would imprison Hillary Clinton in office (if he could). This comes despite the fact that there is no evidence Clinton committed a crime in her handling of the email servers, despite lengthy investigations that found evidence of carelessness and dishonesty. That would be a politically motivated prosecution — retribution for daring to run against Trump and attack him during the campaign.

This is everything we feared about Donald Trump. His long history of trying to silence critics with lawsuits, his inability to let personal slights go, his pettiness: The nightmare scenario is that these would incline him to use the power of the presidency to forcibly silence his critics and opponents. That’s what is done by tin-pot dictators spanning the globe from North Korea to Zimbabwe. That’s what happens in countries where peaceful transitions of power are the exception, not the rule.

Donald Trump just threatened to bring that to America.

Watch: Trump is running for dictator, not president