Governor Jeb Bush greets supporters at the Iowa State Fair in Des Moines, Iowa. (Charles Ommanney/The Washington Post)

— Former Florida governor Jeb Bush took to the stage in Iowa on Saturday a humbled man.

“Iowans are discerning voters,” Bush told some 2,000 potential caucus-goers at the Iowa GOP’s Growth and Opportunity Party on Saturday. “They’re informed voters, they’re nice, and they treat you with respect.”

“Poll numbers go up, and they go down,” he added. “When they go down, you don’t insult Iowa voters because they are the same discerning voters.”

It has been a tough week for the man who many expected to be the candidate to beat in the GOP primary. He admitted, readily, that his performance during Wednesday night’s much-maligned CNBC debate left him weakened.

Republican presidential candidate and former Florida governor Jeb Bush mingles with supporters after speaking at the GOP’s Growth and Opportunity Party in Des Moines on Saturday. (Nati Harnik/AP)

“I say this somewhat in jest, at least there was someone who fared worse in the last debate than me: CNBC,” Bush said amidst a sea of supporters clamoring for selfies.

“I know I have to get better,” he added. “I don’t have this gigantic ego that says, ‘Well they’re just stupid. Iowa voters don’t understand me.’

“But also, I’m a really competitive guy.”

Earlier in the evening, the man who most believe is his greatest competition, Sen. Marco Rubio (R-Fla.), milled with Iowa voters and welcomed a guest — Sen. Joni Ernst (R-Iowa), who has declined to endorse anyone in the presidential primary before the Iowa caucuses.

“Welcome to Iowa! Nice to have you back!” Ernst said as they embraced. “Look at all these people!”

If voters are finally starting to pay attention to Rubio, as his campaign suggests, it is helped by the candidate’s obvious affinity for retail politics.

“He’s charismatic,” noted Steven Fox, 58, who came to hear the candidates at the forum. “I saw him in Ankeny about two months ago. He took the time to speak with everyone.”

Sen. Joni Ernst (R-Iowa) welcomes Sen. Marco Rubio (R-Fla.) to Des Moines, Iowa at the Iowa GOP’s Growth and Opportunity Party on Saturday, Oct. 31. Louisiana Governor Bobby Jindal (R) who was also at the gathering speaks to reporters about his take on debates. (Sarah Parnass/The Washington Post)

“I think he can unite people,” Fox added.

Here in Iowa, Rubio supporters say his stock is rising after he survived an attack during the debate by his onetime mentor Bush, but the candidate is sticking to a tried-and-true script.

“We’re doing the same thing that we’ve been doing for the last six months, and that’s just the basics of running a good campaign,” said Iowa state Sen. Jack Whitver, who is chair of Rubio’s campaign in the state.

“The difference is there’s just a lot more people that are ready to commit that have seen enough,” he added. “People that were intrigued and interested and on the fence in the last five days have decided that they’re ready to commit.”

Outside of Iowa, too, the Rubio buzz is escalating. Friday, he nabbed a critical endorsement from billionaire donor Paul Singer, who is wealthy and powerful enough to potentially move millions into his camp.

At the forum, Rubio disappeared from the room just before Bush was scheduled to speak. Later, amid a sea of journalists and supporters, Rubio was rushed to his car to make a commercial flight out of Iowa after two days of campaigning.

Absent on Saturday were businessman Donald Trump and retired neurosurgeon Ben Carson, who are vying for the lead in the Iowa polls. Ohio Gov. John Kasich also did not appear.

For candidates struggling to get momentum with voters, Wednesday night’s chaotic debate on CNBC has become the newest front in their fight against the much-maligned “establishment,” within the media and their own party.

Sen. Ted Cruz (R-Tex.) made the issue his standout moment on the debate stage Wednesday, and it was one of the most well-received portions of his speech at the Iowa forum.

“How about instead of a bunch of attack journalists, we actually have real conservatives” moderate debates, Cruz said, before name-checking several conservative pundits including “Fox News” host Sean Hannity, and radio hosts Rush Limbaugh and Mark Levin.

Louisiana Gov. Bobby Jindal, whose polling performance has relegated him to the smaller, undercard debates, complained that the Republican National Committee should put all candidates on the same stage.

“The whole process is broken, and I think it started with the RNC and the networks trying to limit the number of debates, trying to limit who is there,” Jindal said. “I think it’s clear they were trying to protect the establishment.”

But other candidates are against the strategy of rallying the conservative base by working the referees, noting as New Jersey Gov. Chris Christie did, that the party’s nominee will be forced to answer tough questions in a general election debate, potentially against Democratic front-runner Hillary Rodham Clinton.

“I’m not one of these complainers about this, okay,” Christie said. “You set up a debate, I’ll show up. I’ll answer whatever questions you have, and if I think they’re stupid questions, like I did the other night, I’ll say it’s a stupid question.

“I just don’t think you get anywhere by moaning and complaining.”