Unlike Obama, whose appearances are carefully choreographed to leave nothing to chance, each of Biden’s public events has an element of suspense. His supporters say his seeming inability to hide his true feelings about an issue speaks to an honesty and candor that are at the heart of his appeal. But White House officials have privately griped about the fallout and distractions when he struggles to stay on message in a highly politicized environment.

“The standing joke in the office is Barack’s learning to speak without a teleprompter, I’m learning to speak with one,” Biden quipped Tuesday at a Jewish American heritage event, managing to be self-effacing while coming close to slighting his boss in the course of a single sentence.

Douglas Brinkley, a presidential historian at Rice University who interviewed Biden for a recent feature in Rolling Stone magazine, said Biden’s become “the Chris Christie of the Democratic Party,” a reference to New Jersey’s shoot-from-the-hip Republican governor.

“Biden’s kind of a joke to the right,” Brinkley said, “but in core Democratic circles, they feel that somehow this longtime Washington politician has packaged himself as the straight talker who’s not hostage to Washington.”

“That kind of makeover doesn’t happen by accident,” he said.