The Daily Show (1996)TV series

When Barack Obama gets called “dude” by a comedian with a fake-news cable program whose audience is a fraction of the size of Johnny Carson’s a quarter-century ago, you know we are deeply mired in an era in which American institutions, from the presidency to the late-night talk show, don’t wield the innate power they once naturally possessed. Authority figures themselves have spent so much time stripping themselves of the garb of authority—losing the tie, rolling up the sleeves, dropping the g’s, Tweeting—that they’ve stripped the authority from themselves as well.

What Jon Stewart did last week in calling the president “dude”—entirely spontaneously, which is why it’s important—was a profound act of...