If Biden stumbles badly between now and October, how would the Democrats replace him?

Historian Victor Davis Hanson writes in part in American Greatness,

...Biden’s cognitive challenges are increasing geometrically, whether as a result of months of relative inactivity and lack of stimulation or just consistent with the medical trajectory of his affliction. His lot is increasingly similar to historical figures such as 67-year-old President William Henry Harrison, William Gladstone’s last tenure as prime minister, Chancellor Hindenburg, or Franklin Roosevelt in late 1944—age and physical infirmities signaling to the concerned that a subordinate might assume power sooner than later.

...When asked questions, Biden’s answers so often reveal racist subtexts. A few days ago, CBS reporter Errol Barnett, who is black, asked Biden whether he would take a cognitive assessment exam. Biden fired back to him that such an unfair question would be as if he had asked Barnett whether he was getting tested for cocaine before going live. “That’s like saying,” a perturbed Biden exclaimed to Barnett, “before you got on this program, you’re taking a test whether you’re taking cocaine or not . . . What do you think, huh? Are you a junkie?” Note the tell-tale Biden trademark of racist insinuation delivered with punk-like braggadocio.

...The problem is that in the past, a cognizant Biden was already racially edgy with his various earlier-career riffs about inner-city criminals, blue-collar chest-thumping about busing, and his more recent ideas about donut shops, accomplished black professionals on the verge of returning to slave status (“put y’all back in chains”), his racist descriptions of candidate Obama’s supposedly exceptional personal hygiene and ability to speak well, his corn-pop braggadocio, and on and on.

His mental lapses now serve as force multipliers and accelerants of the old Biden’s foot-in-mouth disease and render him often a caricature of a racist.

...If Biden late in the campaign stumbles in the debates, there is no post-convention remedy to reassure the public he is compos mentis or otherwise can be replaced by a majority consensus. Then the country would be entering something eerily similar to, but far graver than, the McGovern debacle of desperately looking for a new running mate after it was disclosed that an apparently perfectly cognizant Tom Eagleton—his running-mate for 18 days—had undergone two electric shock treatments in his past as well as undisclosed prior hospitalizations for bipolar disorder.

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