Joe Biden is perfectly capable of having long discussions about the details of legislative proposals and knows his stuff.

Joe Biden is also turning 79 this week, and sometimes stumbles, loses his place or mangles his words.

That’s hardly shocking from a long-winded pol who even in his prime was a self-described gaffe machine. And of course he’s lost a step or two.

But I’ve never understood the efforts by some Republicans and conservative pundits to paint the president as a doddering fool whose White House is actually run by other people.

Given the country’s mounting problems — inflation, supply shortages, border crisis, continuing Covid, in the wake of the Afghanistan debacle — why wouldn’t it be in the opposition’s interest to blame the guy at the top?

They could also make a case that aside from Biden’s undeniable victory on infrastructure, he ran as a moderate Democrat but is now promoting a Bernie agenda. With the president trying to push through nearly $2 trillion more in spending after the trillion-dollar bipartisan measure, he can be attacked as a captive of the party’s left wing.

President Joe Biden speaks during a visit to the NH 175 bridge over the Pemigewasset River to promote infrastructure spending Tuesday, Nov. 16, 2021, in Woodstock, N.H. (AP Photo/Evan Vucci)

President Joe Biden speaks during a visit to the NH 175 bridge over the Pemigewasset River to promote infrastructure spending Tuesday, Nov. 16, 2021, in Woodstock, N.H. (AP Photo/Evan Vucci)

But not as someone who doesn’t know what’s going on.  

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Politico has now given new mainstream credibility to these is-Biden-senile attacks--in the form of a poll. Which is a safe way to say hey, we’re just sampling public opinion--except that news organizations make editorial judgments about what questions to include.

In the survey with Morning Consult, Politico says voters harbor "increasing doubts" about Biden’s health and mental fitness.

Indeed, 48 percent of those questioned say Biden is not "mentally fit" to be president, and 46 percent say he is. Yet last October, voters thought he was fit by a 21-point margin.

On a related question, 50 percent disagree that Biden is in good health, while 40 percent say he is. On that point, I don’t think his regular bouts of coughing have helped.

But here’s the key: 78 percent of Democrats either strongly or somewhat agree that Biden is mentally fit. And 86 percent of Republicans--76 percent of them strongly--say the president is not mentally fit. (A troubling sign for the White House: 47 percent of independents also disagree that he’s fit.)

So this is driven by the same deep partisan divide we see in almost every poll. Most Democrats give Biden the benefit of the doubt, and most Republicans absolutley do not.

June 23, 2021 - Washington, DC, United States: U.S. Representative Alexandria Ocasio-Cortez (D-NY), U.S. House Speaker Nancy Pelosi, a Democrat from California, Senator Charles Schumer. 

June 23, 2021 - Washington, DC, United States: U.S. Representative Alexandria Ocasio-Cortez (D-NY), U.S. House Speaker Nancy Pelosi, a Democrat from California, Senator Charles Schumer.  (Photos by Michael Brochstein/Sipa USA  |  Stefani Reynolds/Bloomberg via Getty Images  |  Photo by Lev Radin/Pacific Press/LightRocket via Getty Image)

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Celinda Lake, a Democratic pollster who has done work for Biden, tried to blame the findings on conservative media and social media, telling Politico: "They’re running a very aggressive campaign on this, and it’s bleeding over into the mainstream a little. By and large, the people who believe this are Trump supporters anyway or they’ve been exposed to the right-wing disinformation machine."

Which gets blamed for everything. But no right-wing "machine" stopped Biden from winning the election, or posting approval ratings in the 50s earlier this year. Republicans and Democrats may well be influenced by consuming media that confirms their opinions. I happen to believe that such questions are largely a proxy for whether you like and agree with Biden or dislike and distrust him.

WASHINGTON, DC - SEPTEMBER 17: U.S. President Joe Biden speaks during a conference call on climate change on September 17, 2021 in Washington, DC. (Photo by Al Drago/Getty Images)

WASHINGTON, DC - SEPTEMBER 17: U.S. President Joe Biden speaks during a conference call on climate change on September 17, 2021 in Washington, DC. (Photo by Al Drago/Getty Images) (Photo by Al Drago/Getty Images)

But the thing about the fitness question is that all Americans get to make up their own minds. Unlike the analysis of complicated issues like climate change or supply-chain disruption, people can rely on their own gut about whether a political leader is up to the job. That’s not a medical diagnosis; it’s pure opinion.

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And they just don’t see that much of Biden other than set-piece speeches where he repeats a lot of the same one-liners (don’t bet against America) and anecdotes (the day his father lost his job).

He doesn’t engage that much with reporters. If he did more of that, he might change some minds. Even though Anderson Cooper’s questions were soft, Biden handled the CNN host and audience at a recent town hall just fine, with the requisite stumbles.

So perhaps the White House is feeding the impression that the president’s own staff wants to limit his public exposure. One poll doesn’t mean Biden has medical issues, but the perception isn’t helpful as he tries to dig himself out of a political hole.