IT WAS the real mistake by the lake. Donald Trump and Joe Biden did everything but bolt from the debate hall and go roll in the mud on the banks of the Cuyahoga River.

The first of three scheduled presidential debates quickly descended into an incoherent brawl that made for tough viewing by anyone looking for a sense of national leadership or purpose from the exercise.

“Trump set the tone for the worst presidential debate in living memory” said the headline over an analysis piece by veteran Washington Post reporter Dan Balz. The Globe’s James Pindell dropped any current-era qualifier, calling it“the worst general election presidential debate in American history.” “A disgusting night for democracy,” was the headline over an Atlantic piece by James Fallows.

Trump and Biden both got in on the effort to badger the other with interruptions and insults, but it was Trump who decided the debate would instead be more of a cage match, dragging the session in the mud from the start and interrupting Biden far more often as he tried to bully his way through the 90 minutes.

“This was the Trump who lives on Twitter, not someone who occupies the highest office in the land,” wrote Balz.

“Is there a single American voter who tuned into tonight’s debate genuinely undecided and is now in Trump’s camp? Are there any voters who were won over by his nonstop bullying and hectoring?” asked the Globe’s Jeff Jacoby.

Biden clearly came prepared to hit back if Trump decided to go low, calling the president at various points a liar, clown, and racist. Exasperated by the constant interruptions, at one point he simply said, “Will you shut up, man?” In between the exchange of verbal punches, Biden looked into the camera at several moments to turn the focus back to what voters are going through, something Trump never even tried to do.

Most pundits seemed to agree that, if anything, the debate slightly helped Biden, if only because it more or less left the race where it stood before Tuesday night — with polls consistently showing Biden holding a lead. Post-debate polls showed voters thought Biden won by a small margin, but the breakdown more or less reflected the candidates’ standing in national polls.

Pindell gave Biden a “C,” saying he seemed tired and unsure in what was hardly a crisp performance. But he said Biden’s team nonetheless has to be happy because “this hot mess of a debate is not likely to change a single poll.”

The old election adage offered up by Boston Mayor Kevin White, among others, implored voters: “Don’t compare me to God, just compare me to the other guy.”

Which is why Biden can live with “C” from a night that his opponent, Pindell says, earned an “F.”

Trump clearly decided to go postal. In what seemed like a Hail Mary from a candidate down in the polls, he hoped doing so would rattle his opponent into doing something that would become the night’s headline.

“But he never rattled Biden,” says Pindell. “So all we are left with was Trump being a bully. Polling is clear on why this is bad. Trump is losing women, independents, and the suburbs because they are tired of his antics. Even his own supporters wish he would tone it down. Trump needs those groups to come around his side. He only gave them more reasons to pick something new.”

As with so many time-honored norms that have been shattered since his arrival on the national stage, Trump came to Cleveland and laid waste to any idea that presidential debates require at least a minimum level of decorum. Whether things ever return to what they once were is now the question.

“I hope there are no more debates before this election. If they happen, I won’t waste another minute of my life watching them,” Fallows wrote. “The modern presidential debate was invented in 1960. We may have seen the end of its useful life this evening.”