AP Photo/David J. Phillip
Marco Rubio.
GOP voters in the focus group called the Florida senator "charming" and "a great orator," praising him as personable and knowledgeable on policy.
In the focus group, 16 people picked Rubio as the winner, four picked Donald Trump, two picked John Kasich, and one picked Ted Cruz, according to Luntz.
When he asked how many of those voters came into the focus group supporting Rubio, only a few raised their hands.
"This was the first debate where they've actually talked about policy issues, and Trump did not look like he belonged on that stage," one voter said.
Another voter also said Rubio seemed "more knowledgeable about the issues."
Despite the overwhelming majority picking Rubio as the winner, voters still couldn't stop talking about Trump.
"I think the reason we're talking about Trump is because he's somebody who's accomplished something, versus just an orator," one voter said. "Maybe Rubio was the best orator tonight, ... but can he accomplish things?"
Someone else was happy that Rubio ditched his "mechanical robot" image. And while Trump went after Rubio for regurgitating canned lines, a perception that's hurt his image in previous debates, the attack didn't seem to stick this time.
"This time he was more personable, you know it was, 'Snap. Snap. Snap.' It wasn't something he memorized," the voter said. "It didn't appear that way."
Rubio was also described as "charming."
"He's got a little boyish face, he come across as just that all-American boy," that voter said. "And that's what he did. ... He zinged Trump several times."
Rubio and his fellow Republican presidential candidates went after Trump aggressively and often at the CNN debate in what turned out to be the biggest Trump pile-on yet. Rubio and Cruz each went on the attack against Trump over several issues including taxes, immigration, Trump's history as a reality-television host, and his business career.
Trump has occasionally criticized Luntz.