The Most Important Presidential Debate Ever It was an unmitigated disaster for Biden and a rout for Trump. Democrats will have to face reality.

In the weeks before CNN’s presidential debate I was skeptical of its significance. I didn’t see a dramatic, high-stakes, pivotal showdown coming, only a moderately sized, pro forma moment in a long, drawn-out campaign. The format had too many prohibitions—muted mics, no open discussion, no live audience, no opening statements, no talking to aides during the breaks, no notes on the lectern. This promised something airless, manufactured, hermetically sealed.

Beyond that I doubted we’d learn anything, because I doubted whether either candidate had the ability to expand on his known persona. Joe Biden has moments of blurted thought, but could he really sustain a thought or make an argument that coheres over two minutes? Could he suddenly show command, a true grasp of his own positions?

Could Donald Trump demonstrate that returning him to power wouldn’t be a wholly irresponsible act? Could he make any dent in the doubts, grounded in history, as to his nature and character? This wasn’t a question about whether he’s grown but about whether he can control himself.

Still, as a national event the early debate would function as the formal kickoff of the campaign, replacing Labor Day. And it would make clear how each candidate intends to present himself and his issues the next four months. So maybe it would be more consequential than I anticipated.

It was in fact as consequential as any presidential debate in history, and the worst night for an incumbent in history. It was a total and unmitigated disaster for Mr. Biden. It was a rout for Mr. Trump. It wasn’t the kind of rout that says: If the election were held tomorrow Donald Trump would win. It was the kind of rout that says: If the election were held tomorrow Donald Trump would win in a landslide.

It is impossible to believe that the Democrats will continue with Mr. Biden as their presidential standard-bearer. They are going to have to do what they fear to do: make themselves uncomfortable, reveal their internal splits and brokenness, and admit what the rest of the country can see and has long seen, that Mr. Biden can’t do the job. They have to stop being the victim of his vanity and poor judgment, and of his family’s need, and get themselves a new nominee.

From the moment he shuffled out with a soft and faltering gait, you could see how much he has declined. He was pale and waxy, and there was something almost furtive in his gaze. His voice was hoarse and feathery, with no projection. His answers were scrambled, halting. At some points he made no sense. At some points he seemed out of it.

Mr. Trump came across as calm, sure-voiced, focused. His demeanor wasn’t insane. He was low-key but high-energy. He obeyed the rules, amazingly, to his benefit. He showed respect for the moderators. If not quite genial he was collected, and he offered a new tack on why he’s running: He didn’t want to, but Mr. Biden, unfortunately, is such a disaster that Mr. Trump has to come back and save the country. “His policies are so bad . . . he will drive us into World War III.” World leaders neither respect nor fear him.

In the split screen, when not talking, Mr. Biden’s face seemed to freeze, sometimes in unfortunate loose-jawed expressions.

Mr. Trump was self-disciplined and knew his arguments. Won’t his proposed tariffs be inflationary? No, they’ll just spur dynamism and growth. He scored Mr. Biden on inflation, and the disastrously executed withdrawal from Afghanistan. He had the president on the defensive on abortion.

After Mr. Biden mumbled “We beat Medicare,” Mr. Trump said, “He did beat Medicare. He beat it to death.”

Just before the half-hour mark, Mr. Trump unleashed an onslaught on illegal immigration and the border. It was pointed, tough and merciless. Mr. Biden had no answer. Or no answer you could follow. Instead he focused on a Trump aside. “Veterans are a hell of a lot better off” under him. “My son spent a year in Iraq.” His greatest hits. It seemed old and sad. Mr. Trump had just handed him his head on the border, and Mr. Biden had nothing to say.

“The whole world is blowing up because of him,” Mr. Trump said. Mr. Biden’s mumbled reply was neither memorable nor coherent.

The moderators turned to Jan. 6. What do you say to voters who say you violated your constitutional oath on that day, and will do it again? Mr. Trump used his reply to tee off a long attack on Mr. Biden and how the world had deteriorated under him. He claimed that he only asked people to move forward “peacefully and patriotically” on that day, and then scored Nancy Pelosi for not accepting his help. “And she now admits she turned it down.”

Mr. Biden said Mr. Trump “encouraged those folks who went to Capitol Hill.” During the riot he sat back and watched it on television. Then Mr. Biden seemed to lose his focus—on what should have been his most powerful case against Mr. Trump.

Mr. Trump accused Democrats of allowing endless riots after George Floyd’s death and said the “unselect committee” on Jan. 6 operated dishonorably.

Mr. Biden often looked at Mr. Trump and seemed to think his facial expression at those moments was powerful. I don’t think Mr. Trump ever looked at Mr. Biden, only at the moderators. He did his own greatest hits: “My retribution is going to be success.” “His son is a felon.” “I did nothing wrong.”

Mr. Biden attempted to bait him with little effect. “Having sex with a porn star while your wife was pregnant.” “You have the morals of an alley cat.” Mr. Trump didn’t get rattled or angry but defended himself: “The public knows it’s a scam.”

He calmly claimed that he has always opposed political violence. A moderator asked if Mr. Trump accept the results of the election. Mr. Trump responded with his usual caveat: “If it’s fair and legal and a good election—absolutely.” “There’s nothing I’d rather do.”

Here, toward the end, Mr. Biden finally had a strong moment. “I doubt if you’ll accept [the November outcome] because you’re such a whiner.” “Something snapped in you” after losing in 2020.

All the fact-checkers will be out this weekend. Good, fine. Mr. Trump played fast and loose—we know this. But he’s the one who’ll have made sense to people. You could hear him and understand what he was saying. He seemed focused. He didn’t seem unstable. Again, he didn’t seem insane.

In pushing and agreeing to an early debate, Mr. Biden’s White House and campaign advisers took a big swing. They missed. Mr. Biden couldn’t execute their plan. The Democratic Party doesn’t know it, but it got a gift. The dam broke. There is still time, and Mr. Trump is still takable.

This can’t continue. I am sorry to say this harsh thing, but allowing him to go forward at this point looks like elder abuse.

At the very least you can be sure that Donald Trump will never bother to debate Joe Biden again. He doesn’t have to. He’ll be only too happy to leave it exactly where it is.