“He looks perkier,” said my nine-year-old, passing the screen as I watched footage of Joe Biden speaking on the first day of the Democratic national convention in Chicago. The president did, indeed, look perkier, borne aloft by the gratitude of 23,000 people in the hall and the millions beyond it for the fact he is no longer seeking re-election. By itself, this moment would have lifted the occasion above the norm. But the Democratic convention this year is so uniquely dramatic, so unprecedented in US history, that it rivals and possibly outstrips even President Obama’s nomination in 2008. And Biden’s heart-wrenching appearance was just the beginning.

“When we fight, we win,” said Kamala Harris in her opening speech on Monday…