Sen. Dick Durbin’s vote in November 2024 against arms sales to Israel was an ominous sign for the Jewish state’s supporters in America. Durbin had always been reasonable on the issue and never flirted with the politics of the Squad, and he was also an institutionalist not a revolutionary—which made sense, because as the Democratic Party’s Senate whip, he was the second in command. Yet it’s hard not to think of that vote when reading the news that, as expected, Brian Schatz has secured his place as Durbin’s successor as whip. That part is less important than what it sets...