Christie and DeSantis promptly attacked Trump for skipping the debate.

Former Gov. Chris Christie of New Jersey used his first answer of the debate to attack the absent former President Donald J. Trump.

Gov. Ron DeSantis of Florida soon followed.

The two candidates went right at Mr. Trump for skipping a second debate in a row, painting him as cowardly and as skirting the democratic process.

But Mr. Christie was equipped with more than one canned attack. After the first commercial break, he turned directly to the camera in the middle of an answer to address the former president.

“Donald, I know you’re watching, you can’t help yourself,” Mr. Christie said. “You’re not here tonight, not because of polls, and not because of your indictments. You’re not here tonight because you’re afraid of being on the stage and defending your record. You’re ducking these things, and let me tell you what’s going to happen. You keep doing that, and no one up here is going to call you Donald Trump anymore. We’re going to call you Donald Duck.”

Mr. Christie had issued a similar taunt early in the debate, saying that Mr. Trump “hides behind the walls of his golf clubs.” His quip was quickly echoed by Mr. DeSantis.

“Where’s Joe Biden?” Mr. DeSantis said. “He’s completely missing in action from leadership. And you know who else is missing in action? Donald Trump is missing in action. He should be on this stage tonight. He owes it to you to defend his record, where they added $7.8 trillion to the debt, that set the stage for the inflation that we have.”

That Mr. Christie would immediately criticize Mr. Trump is no surprise, as he has made attacking the former president central to his campaign. He did so again minutes later, saying Mr. Trump had built only 52 miles of a wall along the southern border.

But Mr. DeSantis’s attack was a marked change from his posture in the first debate, reflecting an effort to draw more stark contrasts with Mr. Trump.