It was never exactly a shock that George Clooney — a lifelong Democrat, and about as Hollywood as they come — would endorse Hillary Clinton for president. But it wasn’t a given, either. And as Donald Trump was bulldozing his many Republican rivals in the spring of 2016, Clinton was still slogging through her own primary contests with Sen. Bernie Sanders (I-Vt.). So Clooney laid out his endorsement that March in a short, to-the-point fundraising letter. He called Clinton a “voice of tolerance and experience,” a champion for the poor and a savvy diplomat. “If ever there was a time...