Joe Biden is more unpopular than Donald Trump. The Democrats’ upstairs-downstairs coalition frays, riven by the Israel-Gaza war, crisis at the US-Mexico border and inter-generational tensions. The party convention in Chicago in August carries the potential for a repeat of 1968. Then, pandemonium in the Windy City helped cost Hubert Humphrey the White House. But for sustained Republican efforts to gut reproductive rights, a strong issue for Democrats to run on, Biden and Kamala Harris would be in even deeper trouble. Even on the economy: strong GDP numbers and an invigorated bull market have yet to yield political profit. After...