Bush’s loyal supporters, including some longtime friends, were aghast at the candidate they saw on the television screens. Gone, they said, was the optimistic message of economic empowerment that was to be the foundation of his campaign. Gone, too, was the confident competitor who dominated Florida politics during his two terms as governor.

“When I see that debate, I don’t know who that man is,” Ana Navarro said on CNN. “That’s not the guy I’ve known for 25 years.”

One Bush fundraiser, who like others spoke on the condition of anonymity to be candid, said the attack on Rubio “was just not the image and the right tone of the person whose campaign is built on ‘the right to rise,’ not the right to step on your protégé to get to the top.”

Rick Wilson, a Florida-based strategist unaffiliated with a candidate, said: “For weeks, the money guys were with Jeb. Last night, those people were telling me, ‘I’m calling Marco’ or ‘I’m done’ or ‘That was absurd’ or ‘I’m finished.’ ”