The second presidential debate was even more dispiriting than the first. Perhaps we shouldn’t be surprised, since the candidates are the same, and neither the issues nor their positions have changed. Donald Trump still hasn’t learned anything about the things presidents are supposed to understand, and Hillary Clinton hasn’t had the personality transplant her constant critics seem to demand.

But the stakes are too high to let ourselves fall into false equivalences. Trump and Clinton aren’t two sides of the same coin. Clinton is a conventional candidate and a conventional debater. She burnishes the truth sometimes to make herself look better. She occasionally falls into a recitation of talking points instead of answering the questions. She came to the fight armed with practiced bromides and a few zingers.

There’s nothing conventional about Trump. His ignorance of public policy is profound. When forced to address a topic with something more than a one-liner from his rallies – health care or the crisis in Syria, for instance – he gets lost in adjectives, incoherence and bluster. Everything anyone has ever tried is a disaster. Whatever he does to fix it will be easy and fantastic. Where did previous attempts fall short? How will he solve complex problems? Trump hasn’t a clue, and shows no signs of having thought hard about it.

Then there are Trump’s brazen lies, which have kept fact-checkers busy and frustrated since his campaign began. Sunday night they came in rapid bursts. No, insurance premiums haven’t gone up as much as Trump says. No, the U.S. doesn’t have the highest taxes in the world; not even close. No, Clinton’s 2008 campaign did not promote the “birther” lie about Barack Obama; Trump did. No, he was not publically opposed to the invasion of Iraq. Trump’s misstatements of fact have been pointed out over and over, but it doesn’t matter. He doesn’t learn and isn’t interested in the truth.

Trump said so many outrageous things that’s it’s impossible to give each its due. He even rebuked his own vice-presidential nominee’s criticism of Russia for presiding over a human rights catastrophe in Aleppo, Syria. And he dragged the campaign deeper into the gutter, defending his lewd remarks about women by attacking his opponent’s spouse.

But Trump brought something to this debate he hadn’t used in their previous confrontation, something without precedent in American presidential politics. He promised, if elected, to use the law enforcement powers of the president to prosecute his opponent. Trump doubled down on the “lock her up” chants heard at the Republican convention.

That’s not how democracies work. Throwing the opposition leaders in jail is for dictatorships and banana republics. Either Trump doesn’t understand the idea of keeping politics out of the justice system or he just doesn’t care. Either of those possibilities disqualify him for the presidency.

What’s most discouraging about Sunday’s debate is the number of viewers who think Trump won. That shows how low were the expectations people had for the Republican nominee. In every aspect you could measure – substance, poise, delivery, judgment - Clinton outperformed her opponent.

Trump still holds onto his disgruntled base, but for other Americans, including a growing number of Republicans, his campaign has become a national embarrassment.