As "Joe Biden" and "senility" become twins in voters' minds, like macaroni and cheese, I figure that many Democrats and liberal pundits — from Sen. Cory Booker to MSNBC's Andrea Mitchell and Joe Scarborough — are trying to forget that in the past several months, they've wondered aloud if Biden, 77, frail, rambling and in obvious decline, is fit for the presidency.

"I just wonder," Scarborough asked after a particularly disastrous Biden debate performance. "Are we afraid to say that a lot of his sentences don't make sense, that he's having trouble completing his thoughts?"

If Democrats weren't afraid then, they're afraid now.

The Democratic Party establishment will limit Biden's exposure to journalists and protect him from Bernie Sanders, 78, who does not show any signs of faltering. Over Sanders' objections, tonight’s CNN debate format has been shaped to favor Biden. The candidates will sit down rather than stand toe-to-toe. Due to the coronavirus, there will be no live audience, and they will take questions, whether from the public or from journalists had not yet been established.

But never fear, my liberal friends, if you're looking for talking points to defend Biden, they were set forth in the left-leaning Politico: Naturally, it's all Trump's fault.

"Trump and GOP mount coordinated campaign to paint Biden as senile," went the headline

The subhead was pure pro-Joe: "The president settles on a schoolyard strategy to take out his likely general election opponent."

It is true that Trump has pushed the theme of Biden's mental fitness relentlessly. But it is also true that Democrats and media, stunned by Trump's victory over Hillary Clinton in 2016, pushed the theme of Trump's mental fitness relentlessly, publicly discussed whether Trump was insane, and openly advocated using the 25th Amendment to remove Trump from the presidency. That failed.

Trump finds a weakness and picks at it. In this he's no different from Barack Obama or the Clintons. You may not like it. But you may have heard of it. It's called politics, and it ain't beanbag.

The truth is that Trump isn't the first to pick at the Biden weakness. Democratic candidates and pundits could see Biden slipping. Booker, U.S. Rep. Tim Ryan, Scarborough, Mitchell, and on and on, all at one time questioned whether Biden had the mental acuity. But now the party and pundits fall in line, to protect their access to power. This, too, is politics.

Not everyone agrees with me. For balance I called on Michael Golden, a center-left Democrat and the author of "Unlock Congress."

He's run tough campaigns. And he thinks there was a time when Biden's gaffes mattered, when swing voters mattered. But he doesn't think swing voters matter as much as they once did. It's all about tribes now.

"Voters' passionate support for Biden or Trump won't be the reason one of them wins," Golden said. "If Democrats' recent wins in the midterms and in state elections in Virginia, Michigan, Wisconsin, Kentucky and Pennsylvania are any indication, then negative partisanship and demographics were always going to matter far more for them in 2020 than any missteps by Joe Biden."

I respect the analysis, but I think swing voters still matter. And that they care about the mental state of their president.

I'm not mocking Biden. Those of us who have parents of his age and older know what we're looking at. It happens slowly. But it happens.

Not to everyone. It doesn't happen to the lucky ones. But it happens.

John Kass writes for the Chicago Tribune.