WASHINGTON -- Donald Trump continues to hold on to his lead in Iowa, but the most surprising element in a recent poll was a surge into second place by retired neurosurgeon Ben Carson. A CNN poll conducted after the debate puts Carson in second place with support from 14 percent of respondents, behind Trump with 22 percent.

Wisconsin Gov. Scott Walker had been enjoying the No. 2 spot in the polls. Before Trump exploded onto the scene, Walker was even placing first in some Iowa polls.

But the CNN poll -- conducted after the first GOP primary debate last Thursday -- found Trump still holding his lead and Carson gaining ground. Trump gave a heated debate performance, including engaging in a much derided exchange with moderator Megyn Kelly of Fox News. Many pundits were quick to dismiss Trump’s chances after the debate, but consistently polls in Iowa have shown no damage to his position in first place.

While few national polls have been released since the debate -- and none that involved live interviews, considered the gold standard in polling -- several independent polls in Iowa show Trump with a solid hold on first place.

Trump's popularity continues to reinforce the growing consensus that Republican voters are looking for candidates who have few or no ties to Washington. Neither Trump nor Carson has ever held elected office. They’ve never run for one before, either.

Another big gainer in the polls was former Hewlett-Packard CEO Carly Fiorina, one more Washington outsider who has never held elected office -- although she did run unsuccessfully for a U.S. Senate seat in California. Fiorina received backing from 7 percent of poll respondents, placing fourth behind Texas Sen. Ted Cruz.

Fiorina’s performance at last week's early debate was the most highly praised. Fiorina wasn’t even allowed on the main debate stage and had to participate in the earlier forum because at the time she was struggling to poll above 1 percent. But the added attention from her well-received appearance appears to be pushing her into the GOP's top tier in the polls.

As for the biggest tumble, that might have been taken by former Florida Gov. Jeb Bush, who took only 5 percent of the vote in the CNN poll. After announcing his candidacy, Bush was frequently polling in second place in Iowa. But the CNN poll put him in seventh place.