Jeb Bush stumbled through a familiar question about his brother and father, struggling for the right words as he cracked a joke about duking it out with anyone who questioned the legacy of his aging dad.

Gov. Chris Christie of New Jersey awkwardly said aloud what many have been wondering about his candidacy: “Am I washed up?”

And Senator Lindsey Graham of South Carolina reached back to the 1990s to attack Hillary Rodham Clinton’s credibility by dredging up her husband’s dishonesty about a sexual affair.

Mischievously promising to translate “Clinton-speak” for the audience, Mr. Graham explained, “When Bill says, ‘I didn’t have sex with that woman,’ he did.”