Retaining Democratic control of the Senate was a tough climb even before the debate. Democrats, who hold a one-seat majority, are defending 23 seats to Republicans’ 11. The Democrats’ races include three seats in states that Trump won in 2020 (Jon Tester in Montana, Sherrod Brown in Ohio and the seat being vacated by Joe Manchin III in West Virginia) and five in states that Joe Biden won by three points or less. A Senate that remains in Democratic hands is conceivable but increasingly unlikely.

The House is a different story. The chamber is divided 220 Republicans to 213 Democrats, with two vacancies; Democrats need just four seats to regain the majority. Of the Republican-held seats, 17 are in districts Biden won. So, Minority Leader Hakeem Jeffries (D-N.Y.) holding the speaker’s gavel in January is a distinct possibility.

And that is where Bennet’s point becomes so important. A Democratic House would be a firewall — the only firewall — against Trump and Trumpism in a second term. It is horrifying to imagine what would happen without it — and that has to be a factor in the party’s deliberations about President Biden’s future.

We’ve been here before during the first two years of Trump’s term, but with a difference: Then, much to Trump’s frustration, Senate Majority Leader Mitch McConnell (R-Ky.) retained the filibuster — he didn’t have the votes to kill it, actually. Does anyone think the next Republican Senate will keep the 60-vote threshold in place? Me, neither. Another check on presidential power, gone.

That would leave the House. On immigration, on tax cuts, on Social Security and Medicare, on climate change, on NATO withdrawal — on any legislative issue out there, Democrats would be the only check. Think about the craziness of the current House majority and what it could do in league with a filibuster-free Senate and a Trump White House.

“It’s a disaster if Trump is president, and it becomes more of a disaster if there’s no legislative body to slow him down on the things he needs legislatively,” a senior House Democrat told me Wednesday.

Here is where the self-interest of House Democrats aligns with the national interest. Most of them are in safe seats, but all of them crave returning to the majority — and my reporting suggests that a majority believes Biden being the nominee makes this less likely.

This is the subtext of former speaker Nancy Pelosi’s comments Wednesday that “it’s up to the president to decide if he is going to run,” as if Biden had not made clear his intention to stick it out. Pelosi’s message to the troops: This isn’t over.

And it is why I was so pleased to hear Bennet emphasize the scope of what is at stake in November, which is at once obvious and underappreciated. He stopped short of calling for Biden to withdraw, but his implication was clear.

Bennet is no bomb-thrower. He’s smart (a Yale Law School graduate and editor in chief of the Yale Law Journal) and politically savvy (a former head of Senate Democrats’ campaign arm who ran for the presidency in 2020). He is decent and committed, responsible and moderate — a person to be taken seriously.

I recall a visit with him at his Senate office early in the Trump administration, when Bennet, his coffee table piled high with books, began reading aloud from Sinclair Lewis’s 1935 dystopian novel, “It Can’t Happen Here,” about Buzz Windrip, a dangerously demagogic senator elected to the presidency.

Bennet was worked up about the uncanny resemblance between Windrip and Trump — and the supine acceptance of his Republican colleagues. He could not believe this was happening — and it was clear, Tuesday night, that he could not believe it was about to happen again.

If, as Bennet is suggesting, Trump is headed back to the White House, it is essential to maintain a bulwark against complete Republican domination. And that requires a clear-eyed assessment, right now, of where this race stands and what can best be done to protect the country.

Because we now know, it can happen here. Except this time, it will be worse.