Sen. Elizabeth Warren, D-Mass., surged ahead of former Vice President Joe Biden in a new poll of likely Iowa Democratic caucus-goers released late Saturday, with Sen. Bernie Sanders, I-Vt., and South Bend, Ind. Mayor Pete Buttigieg slipping into a distant third and fourth, respectively.

The Des Moines Register/CNN/Mediacom poll showed Warren as the first choice of 22 percent of the voters surveyed, while Biden was the first choice of 20 percent of the voters. By comparison, the Register poll in June showed Biden leading with 24 percent support, nine percentage points clear of Warren and eight points clear of Sanders.

J. Ann Selzer, president of pollster Selzer & Co., told the Register the survey represented "the first major shakeup” of the Iowa race, because: "It’s the first time we’ve had someone other than Joe Biden at the top of the leader board."

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Sanders was in third place with 11 percent support, a five percentage-point drop from the Register's June poll. No other candidate cracked 10 percent of the first-choice vote, with Buttigieg garnering nine percent. That also represents a five percentage-point drop from June.

Warren also had the highest percentage of poll respondents (20 percent) who said she was their second choice in the February caucus. By contrast, Biden and Sanders each garnered 10 percent of the second-choice vote. Warren also had the highest favorability rating of any candidate, with 75 percent of respondents saying they had a very or mostly favorable view of her compared to 66 percent for Biden and 58 percent for Sanders.

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Sen. Kamala Harris, D-Calif., rounded out the top five, with six percent of voters saying she was their first choice. Sens. Amy Klobuchar, D-Minn., and Cory Booker, D-NJ, both received three percent. Rep. Tulsi Gabbard, D-Hawaii, former Congressman Beto O'Rourke, entrepreneur Andrew Yang and hedge fund manager Tom Steyer each received three percent.

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The polling shakeup may not be done, as 63 percent of respondents said they could still be persuaded to support a different candidate. Harris, Buttigieg and Booker could still benefit from late deciders, as 39 percent, 37 percent and 35 percent of poll respondents said they were still actively considering those respective candidates.

The poll came from a sample size of 602 likely Democratic caucusgoers with a margin of error of plus or minus four percentage points. It was conducted from Sept. 14-18.

The most recent Fox News poll of Democratic primary voters nationwide showed Biden with 29 percent support, down six percentage points from his peak in May. Sanders was in second place at 18 percent, up eight percentage points from the previous month's poll, while Warren was on 16 percent, down four points from August.