Thursday night, 26 GOP caucus voters from Des Moines, Iowa watched the third Republican presidential debate.

The candidates they supported as they arrived closely mirrored the latest polls. And this debate had impact. Major impact.

Nearly a third of our voters changed their minds over the two hours, walking into our focus group supporting one candidate and walking out supporting another. And the biggest winners of the night – by a mile – were Marco Rubio, Chris Christie, and Ted Cruz.

The common thread? These three candidates all blasted the mainstream media and CNBC's moderators for bad questions and even worse – bias.

Ted Cruz’s body slam of the media was the single highest result I’ve ever had in any debate from any campaign – ever.

Here are my seven top takeaways:

1. Using the ‘mainstream media’ as the GOP’s bete noire works. Ted Cruz’s body slam of the media was the single highest result I’ve ever had in any debate from any campaign – ever.  Fully 24 of the 26 participants had their dials at 100 – a fete almost impossible because the entire room erupted in applause.  But he wasn’t alone. 

Marco Rubio’s line that “the Democrats have the ultimate Super PAC – it’s called the mainstream media,” caused the group to roar with approval. And Chris Christie scored the trifecta by criticizing the stupidity of a fantasy football question (to Jeb Bush) and then skillfully challenging the moderators for trying to talk over him: “Even in New Jersey, what you’re doing is rude.”

2. Warning: Republicans should not attack other Republicans. Republican caucus and primary voters are much more interested in the candidates attacking the Democrats rather than each other. The three lowest dialed moments of the two-hour debate: 

- Kasich's opening statement when he attacked just about every rival for not being serious.

- Trump’s assault on Kasich for, well, everything...

- Bush’s blitz on Rubio for not showing up for work.   

3. Defeating Hillary Clinton is the GOP’s number one priority. Carly Fiorina gamely picked up the baton on behalf of women, noting that "every policy Hillary Clinton espouses is bad for women.”

Our participants cheered. 

But Christie won the most kudos from our session when he started off the debate by attacking the leading Democrats (“I see a Socialist, an isolationist and a pessimist, and for the sake of me, I can’t figure out which one is which.”) and never let up through his closing remarks. 

4. With such a distrusting and disdainful electorate, humor and humility go a long way. From Carly Fiorina laughing at her own inability to "smile enough,’"to Ted Cruz pointing fun at himself for being “too agreeable, easy going,” just about every joke worked – and the jokes made at the expense of the media worked even better.

Conversely, the most serious candidates at the beginning – Kasich and Bush – had the most trouble by the end. 

5. Voters are now in the "show-me" phase. Both Carson and Trump are leading across the country, but neither won the night. 

Our Iowa caucus voters complained that neither offered enough substance or solutions.

Trump was criticized for being … Trump.  And they were nervous that Carson’s cool, calm demeanor wouldn’t be strong enough to stand up to the Democrats. 

6. Jeb Bush IS a nice guy, and nice guys finish last. He needed a game-changing performance last night… but he didn’t produce it. What he did produce was one of the lowest dialed answers of the night, attacking Rubio for his Senate voting record, and later when he said we should regulate fantasy football.  Plus, it set up Christie to deliver one of the most blistering attacks on the moderators for asking such a stupid question.     

7. Moderators should be seen but not overly heard. It wasn’t just the topic and tone of the questions that Republicans rejected. It was the length of questions that rattled viewers. Participants began to time the questions, and some took longer than the allowable answers. 

CNBC was the big loser of the evening.

Frank Luntz is a pollster and political consultant. He is founder and president of LuntzGlobal and a Fox News contributor.