Some of Kamala Harris’s biggest donors thought things were looking up on a Tuesday in December 2019: they’d been hearing word of a brand-new super PAC forming to rescue her presidential campaign and that morning the group was placing its first ad on Iowa TV. A few hours later, though, Harris dropped out of the race and the spot never saw daylight. But now, with Joe Biden’s future atop the Democratic ticket in question, a handful of her California fundraisers...