“Undecided voters” are to journalism what “future historians” are to people who routinely invoke them: an imaginary audience that justifies passivity. Journalists love undecideds because focusing on them allows them to pretend that, like that non-audience, they don’t know anything — so they have no obligation to tell the truth. And people who yammer about “future historians” love them for a corollary reason: it allows them to delegate responsibility, so they have no obligation to do anything.