Joe Biden got in a spot of hot water last week over a heroic war story he has been telling on the campaign trail. An extensive Washington Post investigation found the following: "it appears as though the former vice president has jumbled elements of at least three actual events into one story of bravery, compassion and regret that never happened." Biden denied doing anything wrong, telling the Post and Courier that "the central point is it was absolutely accurate what I said."

But the facts of what happened in Afghanistan are in one important sense beside the point. They raise a question: Is Joe Biden mentally unsound? He certainly gives a strong impression of having lost a step or three over the years — and a narrative that his mind is in trouble has already taken shape. If Biden is nominated, his possibly-failing brain will be the Hillary Clinton emails story of 2016 all over again.

Let's just examine two pieces of evidence. Here is Biden seven years ago in 2012, where he easily put away Paul Ryan in the vice presidential debate:

Here is Biden from a few days ago, speaking about his disagreements with Bernie Sanders on health care policy. Watch from about 40 seconds in:

To be fair, this isn't entirely an age thing. Biden has been notoriously gaffe-prone for his entire career. He is also notorious for making up dramatic stories, or exaggerating real ones, especially when they inflate his resume. When he ran for president in 1987 he repeatedly lied about marching for civil rights, even after his aides tried to get him to stop. He's a guy who loves to talk, and doesn't let the facts get in the way of a good story.

But as Hamilton Nolan details at Splinter after attending several Biden rallies, he's also clearly losing some of his verbal fluency. It "is impossible not to notice that Joe is getting old. Any reporter who doesn't note this is not telling you the whole truth about what they witness," he writes. "Biden is not senile, or unable to function, but the signs of the slow creep of cognitive decline are too visible to ignore." Even some attempts to do damage control — like reassurances from Biden's brain surgeon who saved him from two aneurysms 31 years ago that he is in fine shape — are less than convincing.

What's more, Biden produces a steady stream of these embarrassing verbal flubs. At the conclusion of the most recent debate he tried to get supporters to text "JOE" to a number to send him money, but forgot the texting part and nonsensically said "go to Joe 30330" instead. After the shootings in El Paso and Dayton, he referenced "the tragic events in Houston today and also in Michigan" before correcting himself. More than once he has referred to Margaret Thatcher (who died in 2013) as prime minister of the U.K. Here he is talking about his time serving with "Raprock" Obama. There are many similar stories.

If Biden is the nominee, I can all but guarantee that this will be one of the biggest two or three stories of the campaign. He will keep comically screwing up, Trump's campaign and supporters will pounce on and amplify it every time, and political reporters will make it a major focus of coverage. Indeed, they're doing it now — speaking of his verbal confusion as a "real political risk" and discussing how it is "providing new openings for critics[.] It's already a punchline. Biden's campaign, meanwhile, will be repeatedly wrong-footed and frustrated as its policy ideas and attacks on Trump get lost in the ocean of Brain Stories.

I know this because it's exactly what happened to Hillary Clinton with Her Emails — a damaging story that kept getting dribbled out for months and months, with every fresh droplet of news getting saturation coverage. It was probably the most-covered single story of the entire campaign, and did tremendous damage to Clinton's campaign.

It goes without saying that all this is quite unfair. Trump is himself quite obviously losing his mind (listen to him repeatedly say "oranges" when he means "origins"), and besides is the most ludicrously incurious and ignorant person ever to serve as president. It scarcely matters that Trump is incapable of learning what is happening in the government, since he wouldn't bother to do so even if he could. He is also the most corrupt president in history by far, has a mile-long history of alleged sexual assault (including alleged rape), and has governed as a brutal, cruel racist. Glaze-eyed libertarian ideologues, interested parties, and whiny fascist trolls are making policy in the ruins of his administration. It's exactly what anyone could have predicted from the way he campaigned in 2016, which still didn't dent the emails coverage.

But the sheer scale of Trump's scandals and incompetence partly immunizes him from this sort of sustained coverage. No one thing can get sustained coverage when each new atrocity elbows the last off the public stage — and as the emails story shows, repetition is central to how political views are shaped.

It would be nice if the elite political press had learned anything from their horribly botched 2016 coverage. But there is no sign of that happening whatsoever. The Democratic electorate can either nominate Biden and hope the coverage doesn't drag him down to defeat (and that his mental acuity doesn't decline any further), or nominate someone who is still sharp and remove the problem at a stroke. It's up to them.