Alfred Hitchcock explained the nature of cinematic terror with a story about the bomb under the table. People are sitting around a table having a mundane conversation about baseball when — boom! — a bomb goes off, instantly killing everyone. You’ve momentarily surprised the audience.

But what if, Hitchcock asked, we are shown beforehand that the bomb is there?

“In these conditions this same innocuous conversation becomes fascinating because the public is participating in the secret,” Hitchcock explained to his fellow director François Truffaut. While everyone is just sitting around chatting, the viewer wants to shout: “Don’t sit there talking about baseball! There’s a bomb!”

“The conclusion,” Hitchcock said, “is that whenever possible the public must be informed.”

I bring this up because we know there’s a bomb under the table — the threat of a second Donald Trump presidency. And we have a fairly good idea of the crippling destruction that will ensue. Yet here we are, still talking about baseball.

“A shadow looms over the world,” The Economist noted in a recent editorial about the year ahead. “That a Trump victory next November is a coin-toss probably is beginning to sink in.”

Trump’s increasingly authoritarian braying makes his intentions clear: nullifying parts of the Constitution, imprisoning political foes. The Trump who used to obsess about what the mainstream media — even Twitter/X — thought of him no longer does. He doesn’t need to. The Trump who tried to burnish his credibility by stocking his cabinet with establishment Republican stalwarts will no longer risk anything less than proven fealty. There will be no one on the inside leaking or secretly restraining Trump in a second term; Trump has kept track of the names.

Trump’s first term will look benign compared with what we can expect from a second. “The gloves are off,” Trump has declared.

Still, the Democrats act as if everything is normal. They talk about why to support Joe Biden’s campaign for re-election: He has done a pretty good job, they say. He led the country out of the pandemic and avoided a deep recession. He beat all other primary candidates last time. And he beat Trump before. We should go with a proven contender.

But even if Biden has done a pretty good job as president, most Americans don’t see that. His approval ratings have just hit a new low. Biden may want another term, but the obvious if unchivalrous response is, “So what?” Not every person, whether young or elderly, wants what is in his own best interest, let alone in the interest of a nation. Democrats can’t afford to take a version of the “It’s Bob Dole’s turn” approach this time around.

Whatever success Biden had in the primaries and general election last time, we are not in the same place we were in 2020. The pandemic has receded; the animating cause behind widespread domestic protests has changed. We are now entangled in two overseas wars. Several polls show a tossup between Biden and Trump.

“Stop badmouthing Biden,” some Democrats will say, as if acknowledging reality were akin to arming the enemy. But desperate times call for bucking tradition. What we need are extraordinary measures.

That means Biden voluntarily stepping aside — and not automatically backing his vice president either. What we need is a capable, energetic candidate who can lure the Democratic faithful to the ballot while offering a plausible alternative for independents and non-Trumpian Republicans.

And we have options. Representative Dean Phillips of Minnesota has already taken the gutsy step of declaring his candidacy and shown that he’s serious about the effort. A full slate of potential contenders offer the same kind of moderation that propelled Biden to the presidency, but with the benefit of youth and energy: Gov. Gretchen Whitmer of Michigan. Senator Raphael Warnock of Georgia. Transportation Secretary Pete Buttigieg. Even mixed-bag Gov. Gavin Newsom of California or the relatively unproven Gov. Wes Moore of Maryland.

It’s past time to start taking the Trump threat seriously. We can no longer pretend that Biden is the same candidate at 81 that he was four years ago, or that the extraordinary circumstances of 2020 mirror those of today. We can no longer entertain petty comparisons over which Republican primary candidate is less awful, as if any of it matters. There is no more illusion that Trump will slip away, that Republicans will move on from Trumpism or that a parade of indictments or even convictions will make a whit of difference to his most ardent supporters.

When Trump won in 2016, Americans who sat on the sidelines could say in their defense that they were surprised. Nobody had warned them that Trump could actually triumph. Nobody had warned them about what he would do with that presidency — or they just hadn’t noticed the signs. We no longer have those excuses.

We know there is a bomb under the table.