President Joe Biden’s great age and concomitant physical and mental decline have been subjects of intensifying contention since before Democrats first chose him as their leader in 2020. Back then, he was only — only! — 77 years old. Now, he is 81, and if he is reelected, he’ll swear his oath of office at the age of 82. If he makes it through a second term, he’ll quit the White House at 86.