How Donald Trump is coping with his polling slump

Sioux City, Iowa (CNN)  Donald Trump is entering uncharted territory.

After spending more than 100 days perched atop the polls, on Tuesday Trump -- for the first time -- slipped to No. 2 as retired neurosurgeon Ben Carson seized his inaugural first-place finish in a national poll. The move comes just days after he stole the front-runner mantle from Trump in Iowa, a key early voting state.

Stumping Tuesday evening in the Hawkeye State, for the first time since that backwards slide, Trump kicked off his speech to a crowd of nearly 2,400 people by acknowledging his campaign has fallen "a little behind in Iowa."

"Iowa will you get your numbers up, please?" Trump exclaimed. "Will you get these numbers up? I promise you I will do such a good job."

Trump's journey to acceptance of the slide traveled through a mixture of denial and disbelief, before making his way to attack -- his sights trained firmly on Carson.

On the stump this weekend, Trump accused two polling groups of bias when their surveys placed him No. 2. In interviews, though, he accepted the polls' results. Trump told CNN that while he was "really surprised" by the results and said they meant he needed "to work a little bit harder in Iowa."

On Tuesday morning, he simply said, "I don't get it," during an appearance on MSNBC's "Morning Joe."

For a candidate who spends at least 10 to 15 minutes of his stump speech talking up his lead in such surveys, it's an uncomfortable position, one Trump acknowledged in Iowa on Tuesday.

"I'm second, so it's not terrible," Trump said. "But I don't like being second, second is terrible to me."

The slide didn't stop Trump from talking up his poll numbers entirely. This time, he touted his strong numbers when it came to leadership and the economy.

Still, Trump's dip in polls may spell trouble for a candidate who has put so much stock in them.

"One of the reasons you don't brag about your standing in the polls is because when it goes down, you look silly attacking the polls you were praising not so long ago," said Eric Fehrstrom, a political communications veteran who served as senior adviser during GOP presidential nominee Mitt Romney's 2012 bid. "You actually sound stronger when you're the poll leader if you dismiss those polls."

In fact, a common refrain by experienced politicians on the campaign trail is the only poll that matters is the one on Election Day. Trump, meanwhile, has been anything but the typical candidate.

"He's the one that has encouraged everyone to look at the polls as a verification of his standing in the race. So now that those polls are beginning to deflate it's not wrong for people to conclude that he's not as popular as he was back in the summer," Fehrnstrom said.

Former Romney deputy campaign manager Katie Packer said obsessing over poll numbers also just isn't something the 2012 GOP nominee did.

"He let the campaign worry about that. He went out there and delivered his message," said Packer, who is neutral in the 2016 race but is the founding partner of WWP Strategies, which works for Marco Rubio in Michigan. "People don't want to elect a political operative. They want to elect somebody that's a leader and not somebody that's all wrapped up in their status in the polls."

Trump doesn't just bring up his lead in the polls before the thousands of supporters who consistently flock to his rallies, but also in interviews, often when challenged on his controversial proposals or his lack of specifics.

"I'm way, way ahead," he has said, or, "I'm leading in every poll," as if to shield himself from the scrutiny a leading presidential campaign is bound to attract.

R.C. Hammond, who served as GOP presidential candidate Newt Gingrich's press secretary in 2012, said Trump won't altogether lose ground on his platform of being a "winner" simply by slipping in the polls.

"He just needs to find ways to reestablish his credibility as a winner. If he can do that, that's the way he can hold onto voters who will be looking to support the person can they actually win that game," he said.

For that, Hammond said Trump may need to start dropping money on television ads, something Trump has not had to do thus far.

"It's time to put his money where his mouth is," he said.