Before we turn to the upcoming Democratic National Convention, which begins Monday in Chicago, I have to make one observation about the Paris Olympics, which just ended: Is there anything more bizarre than artistic swimming? I am amazed by the swimmers’ athleticism but terrified by the way they look before diving in. That makeup makes them look like homicidal clowns. The nose clips don’t help much, either.

Now, in an admittedly tortured transition, let’s talk about the Democratic convention. It is easy to dismiss these national conventions, Republican and Democrat, as blowhard nonsense, because they are blowhard nonsense. Blowhard will be on full display in Chicago.

But so will excitement as the presumptive nominee, Kamala Harris, continues to ascend to the throne. She is riding on rarefied air and greatly benefiting from the element of surprise that is absent from modern politics: A month ago few liked her, much less thought about her.

But because of the pullout of her boss, Joe Biden, there is a genuine frenzy over her. Her campaigning has exceeded all expectations. Democrats, who tend to be whiny mopes, have never been more energized. Trump has no idea what hit him, his default response of wild accusations worthless. But we still don’t quite know what to make of Harris. Is she real or Memorex? Is she true presidential timber or will the glow wear off? What about border security, which she badly fumbled as vice president? Or the economy, for which her proposals don’t seem very concrete?

With millions watching, this is a pivotal test for Harris. A lousy speech will stop momentum. A mediocre speech will slow momentum. A great speech will make Harris unbeatable, rising to the occasion like a handful of previous candidates have: F.D.R. in 1932, with his New Deal; Richard Nixon in 1968, talking about “forgotten Americans”; Barack Obama in 2004, with “There is not a liberal America and a conservative America. There is the United States of America.”

We should also add to the list: Donald Trump in 2024 at the recent Republican convention, in Milwaukee, talking about what Biden looks like in a bathing suit:

“Somebody said he looks great in a bathing suit, right? And you know, when he was in the sand and he was having a hard time lifting his feet through the sand, because you know sand is heavy, they figured three solid ounces per foot, but sand is a little heavy, and he’s sitting in a bathing suit. Look, at 81, do you remember Cary Grant? How good was Cary Grant, right? I don’t think Cary Grant, he was good. I don’t know what happened to movie stars today. We used to have Cary Grant and Clark Gable and all these people.”

Presidential …

Modeling ear fashions at the Republican National Convention.

Harris’s speech will be a defining point, but the days of unpredictable conventions are over. Brokered conventions, in which no candidate had a majority on the first vote, used to be frequent. They resulted in backdoor deals by ham-fisted power brokers in smoke-filled rooms, with cigars, ample whiskey, and incorrigible egos. They were raucous and naturally corrupt. Rules were ultimately altered to provide for more public representation, which, obviously, was good. But the dynamics have changed.

Blowhard will be on full display in Chicago.

Now, conventions are marathon infomercials in which each party extols its supposedly sacred virtues. Occasionally a great speech comes along, such as the one Obama gave, which set in motion his ultimately successful bid for the presidency. Most of the time they are too long and windy, although they are helpful in revealing the worst of a candidate.

Trump started off O.K. when he talked about the personal impact of the assassination attempt against him and the need to bring the country together. Then he jettisoned the teleprompter and for the next hour meandered with the sort of disjointed blather that makes Biden sound like Churchill.

I just don’t understand why Trump insists on wearing a red tie that points like an arrow to his allegedly diminutive package: he is no Olympic pole-vaulter. Add to it the shock of fiery orange hair that could roast marshmallows.

There were also the Trump women, looking all alike onstage in Farrah Fawcett–style blonde hairdos with a little flip at the end. The lone exception was Kimberly Guilfoyle, the fiancée of Donald Trump Jr. and a former Fox News host. I cannot begin to unravel what she was going for.

The equally disturbing element of the Republican convention in Milwaukee was watching the attendees on the floor and wondering why they think dressing up like idiots adds to their credibility.

A delegate from Montana in a black cowboy hat covered with political buttons, which made her head look like a pincushion. White patches over the ear in reference to the wound Trump received. A woman dressed in a Revolutionary-era costume. (I wish I had been with her when she decided to wear this.) The Texas delegation in white hats, a metaphor for their pristine vision of the country.

The costumes and accessories seriously disturbed me. They were not clever or even funny but a scary vision of the country. The attendees’ white and pasty faces sticking out from their gizzard necks made them look like the inversion of Al Jolson’s infamous blackface. I began to wonder if they used shoe polish normally reserved for white bucks.

J. D. Vance and the Trumps: not an obscure 1950s doo-wop group.

I do have a fear that the Democrats won’t be much better. But based on pictures of past conventions, they seem actually interested in politics and the future of the country rather than outright buffoonery. There are some disturbing images from the Democratic convention in Chicago in 1968—Mayor Richard Daley angrily shaking his fist on the convention floor, looking like a pit bull; legendary television correspondent Mike Wallace being forcibly removed; the incomprehensible scene outside where Chicago police officers were beating people protesting the Vietnam War and the nomination of Hubert Humphrey.

I imagine there will be some in prison costumes, expressing the desire that Trump get jail time for at least one of the zillion criminal trials facing him. I do hope all the women present bring their cats to give to J. D. Vance after his comment about childless cat ladies. (Vance, by the way, may be even more dangerous than Trump, given that he knows how to read.)

The Democratic speakers, like the speakers at any national convention, will be inconsistent. The full list has not been issued yet, but press reports said there will be the sublime (Obama), the now revered (Biden), as well as the also-rans (the Clintons, trotted out like statues).

But the star of the show will be Harris, unless she bombs.

I am glad I am not the one doing what she has to do. We should all be glad we’re not doing it.

Good night, and good luck.

If it doesn’t work out, there is always artistic swimming.

Buzz Bissinger is the author of Friday Night Lights and a co-author of Shooting Stars with LeBron James