In the Great 2020 Presidential Debate Debate, each side’s motives are obvious.

For months, Donald Trump’s campaign has been calling for more than the three scheduled televised face-offs with Joe Biden, the presumptive Democratic nominee. It’s no mystery why: Trump is behind in the polls, and candidates who are in trouble want more chances to rally support.

But Trump’s staffers pretend to have more high-minded considerations: The only reason they want the debate calendar expanded, Trump campaign manager Bill Stepien insisted on Monday, is because early voting will have started in 16 states by Sept. 29, when the first debate is scheduled. “That’s a concern to me,” he piously intoned.

In Camp Biden, meanwhile, a rising chorus is urging there be no debates at all. “Whatever you do, don’t debate Trump,” former White House Press Secretary Joe Lockhart bluntly advised Biden last week. Democratic strategist Zac Petkanas agreed, tweeting: “Biden shouldn’t feel obligated to throw Trump a lifeline by granting him any debates.” In his New York Times column, Thomas Friedman argued that Biden should avoid the debate stage unless Trump agrees in advance to release his tax returns and allow “a real-time fact-checking team” to play a role in any televised encounter.

What really worries Biden’s boosters, it’s safe to assume, is that the former vice president increasingly struggles to express himself when speaking extemporaneously, and is apt to come across as flustered and defensive in any debate with Trump. That explains why Biden has agreed to so few unscripted TV interviews, and why he lashes out at suggestions that he take a cognitive test. But what the Biden advocates claim to be concerned about is that Trump will ruin any debates by deliberately telling lies, making it a waste of Biden’s time to appear with him on TV.

Allow me to make a few predictions. The debates will go ahead as planned — three of them, no more, no less. The matchups between the two oldest White House contenders in history will attract more viewers than any previous debates, breaking the record set by the Trump vs. Hillary Clinton clashes in 2016. The broadcasts will prove a huge publicity windfall for the media celebrities selected as moderators.

And none of it will increase voters’ insight into any substantive issue by so much as an iota.

America’s quadrennial presidential debates have become an absurdity. They long ago devolved into shallow “gotcha” contests, prime-time entertainments designed to elicit memorable soundbites — tart put-downs rehearsed in advance or the unforced error of an unexpected gaffe. But under no circumstances are they permitted to bore viewers with a thoughtful exploration of the candidates’ views. It has been decades since a presidential “debate” involved any actual debating. The candidates don’t seek to persuade voters with arguments and evidence. The moderators aren’t interested in facilitating real discourse. And the vast majority of viewers who tune in do so not to learn more about each candidates’ policies, but to root for one and sneer at the other.

Nearly 30 years ago, the renowned columnist Tom Wicker deplored the derisory quality of presidential debates. “These high-stakes showdowns are gushing fountains of misinformation, disinformation, posturing, prevarication, and puerility,” he wrote. That was in 1991, and the showdowns have only become more insufferable and obnoxious since then.

It doesn’t have to be like this. There are numerous ways to raise the caliber and deepen the quality of presidential debates, if that’s what campaigns and voters really wanted. On occasion, I have gone through the exercise of recommending possible reforms. But they’ll never happen. We have frivolous, foolish debates because we have a frivolous, foolish political culture. The former won’t change until the latter does. And the latter won’t change until voters get sick of presidential contests that play to their worst instincts and not to their best ideals.

The Trump-Biden debates will illuminate nothing about this year’s presidential race that Americans don’t already know. They will be just one more cringe-inducing display of the ongoing decline of US leadership before the world’s eyes. But if nothing else, perhaps they can at least encourage voters to consider doing away with these spectacles for good.

Candidates for the White House don’t have to debate, after all. From George Washington’s time through Dwight Eisenhower’s, presidential debates were unknown. Andrew Jackson and John Quincy Adams, twice bitter rivals for the presidency, never squared off on the debate stage. Lincoln and Douglas only debated as Senate candidates. Woodrow Wilson didn’t debate Theodore Roosevelt, Herbert Hoover didn’t debate Al Smith, and Franklin Delano Roosevelt didn’t debate anyone. It wasn’t until 1960, when John F. Kennedy and Richard Nixon agreed to four TV encounters, that the first presidential debates were held. And even then, it took another 16 years before the practice caught on.

Sadly, the quality of the debates has declined with each succeeding campaign. The Nixon-Kennedy bouts were seminars in statesmanship compared with the cynical media circuses of more recent years. The confrontations between Trump and Biden will be the dumbest, tawdriest, most embarrassing to date. Let them be the last.

(Jeff Jacoby is a columnist for The Boston Globe).