evidence: I have an unusual window on Biden’s march toward the precipice. In September, I wrote a column headlined "President Biden should not run again in 2024." It shouldn’t have gotten as much attention as it did, because it said no more than what many Democrats were mulling through last summer. But perhaps because I have been a strong supporter of most of Biden’s foreign and domestic policies, this call for him to step aside created a stir. [...] Biden might have considered withdrawing if Vice President Harris was more popular than he was — running 10 points ahead of him in polls, say. But Harris hasn’t gained traction as vice president, and Biden knows it. Some say Biden deliberately sidelined Harris; I think her shortcomings reflect her own political weakness. But the fact is that Biden had no obvious heir. [...] Biden’s family has played a central role, especially his wife, Jill. When my column appeared last September, I was told by people who know the Bidens well that the president was angry but that the first lady was irate. She’s his protector and advocate — always. His children, Hunter and Ashley, would probably have been comfortable with him stepping aside. But even after Thursday night’s performance, you could see Jill Biden onstage at a "victory" party clapping and leading a chant, "Four more years!"