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Elizabeth Warren has surged in Iowa, narrowly overtaking Joe Biden and distancing herself from fellow progressive Bernie Sanders, the latest Des Moines Register/CNN/Mediacom Iowa Poll shows.

Warren, the U.S. senator from Massachusetts, now holds a 2-percentage-point lead, with 22% of likely Democratic caucusgoers saying she is their first choice for president. It is the first time she has led in the Register’s poll.

Former Vice President Biden, who had led each of the Register’s three previous 2020 cycle polls, follows her at 20%. Sanders, the U.S. senator from Vermont, has fallen to third place with 11%.

No other candidate reaches double digits.

“This is the first major shakeup” in what had been a fairly steady race, said J. Ann Selzer, president of Selzer & Co., which conducted the poll. “It’s the first time we’ve had someone other than Joe Biden at the top of the leader board.”

South Bend, Indiana, Mayor Pete Buttigieg follows the three leaders as the favorite of 9% of poll respondents. U.S. Sen. Kamala Harris of California is at 6%. U.S. Sens. Amy Klobuchar of Minnesota and Cory Booker of New Jersey are at 3%.

Polling at 2% are U.S. Rep. Tulsi Gabbard of Hawaii, former U.S. Rep. Beto O’Rourke of Texas, businessman Tom Steyer and entrepreneur Andrew Yang.

Eight others are polling at 1% or less.

But the race is far from settled: Just one in five likely Democratic caucusgoers say their minds are made up, while 63% say they could still be persuaded to support a different candidate.

“The data in this poll seem to suggest the field is narrowing, but my sense is there’s still opportunity aplenty,” Selzer said. “The leaders aren’t all that strong. The universe is not locked in.”

The poll of 602 likely Democratic caucusgoers was conducted Sept. 14-18, and the margin of error is plus or minus 4 percentage points.

Warren’s steady rise in Iowa

Other candidates have seen their Iowa Poll numbers briefly spike — O’Rourke hit double digits early after running in a competitive U.S. Senate race in Texas, then fell back. Buttigieg surged after a well-received CNN town hall performance, then drops in the new poll. But no one in Iowa so far this cycle has seen Warren's steady and sustained momentum.

The Register’s first 2020 caucus poll, in December 2018, pegged Warren's support at 8%. In March, about two months after she first visited the state and formally announced she would run, that rose to 9%. In June, as Iowa Democrats began to marvel at her organizational strength, she rose to 15% — though that poll’s methodology differed somewhat from the others.

Today, the universe of people who say they are considering Warren in some way — 71% of likely Democratic caucusgoers — is larger than it is for any other candidate.

That includes 22% who say she is their first choice for president, 20% who say she is their second choice and another 29% who say they are actively considering her.

Trailing her are: Biden (60%), Buttigieg (55%), Harris (55%), Sanders (50%), Booker (42%), O’Rourke (38%) and Klobuchar (37%).

It’s also higher than where Warren was polling in June. Then, 61% of respondents were considering her in some way.

“That appears to be a powerful leap forward and suggests that she can improve further, because she’s got these people actively considering her and thinking of her as a second choice,” Selzer said. “She’s got a huge number there. Those people can be converted.”

Warren is the best-liked candidate in the field: 75% of likely Democratic caucusgoers say they view her favorably. Next-best are Buttigieg, who is viewed favorably by 69%, and Biden, at 66%.

But Selzer said Warren’s numbers also reveal some vulnerability.

Among those who say she is their first choice for president, only 12% say their minds are made up, while 88% say they could be persuaded to support another candidate.

More Biden supporters are firm in their choice: 26% say their mind is mind up, with 70% saying they could be persuaded.

Biden and Sanders slip

Biden and Sanders — who have held first and second place, respectively, since last December — have hit new lows, though they still outshine 16 other candidates.

Their numbers aren’t bad, Selzer said, but the downward trend line is troubling.

Overall, the former vice president has slipped in each of the four Iowa Polls the Register has conducted this caucus cycle — in terms of both support and favorability.

In December 2018, 32% of likely Democratic caucusgoers said Biden was their first choice for president. That’s fallen in each poll as Biden reintroduces himself to Iowans — and as his competitors have targeted him as the polling front-runner.

Biden’s favorability rating also has fallen — 82% of likely Democratic caucusgoers had a favorable view of him in December, compared with 66% today. His unfavorable numbers have nearly doubled in that time from 15% to 29%.

Even among those who say Biden is their first choice for president, they’re less enthusiastic than are supporters of other candidates.

Twenty-eight percent of all poll respondents describe their feelings toward their first-choice candidate as “extremely enthusiastic.” But 32% of Warren supporters say they are “extremely enthusiastic” about their choice, compared with 22% of Biden supporters. Biden supporters are more likely to describe themselves as “mildly enthusiastic” (31%) than are Warren supporters (11%).

Biden does best with older caucusgoers, winning the support of 35% of those 65 and older. That demographic makes up about a quarter of likely caucusgoers, and Biden is their top choice, with an almost 3-to-1 lead over Warren.

But he struggles with young people. Just 9% of those younger than 35 say he is their first choice for president. Warren leads that demographic, at 27%.

Sanders, too, has hit a new low overall, falling from a high of 25% in March — just after he announced he would run. He dropped to 16% in June and is at 11% today.

Part of Sanders’ problem: Warren has eaten into some of his key constituencies.

Among those who say they caucused for Sanders in 2016, 25% say they will do so again. Thirty-two percent say they will support Warren instead, and 12% opt for Buttigieg.

Katie Naset, a 37-year-old poll respondent and Clive resident, said she caucused for Sanders in 2016 because he advanced a far-left agenda focused on issues such as “Medicare for All,” student loan debt relief and affordable child care.

“I aligned more closely with him than Hillary Clinton on those issues,” the family law attorney said. “But at this point, Elizabeth Warren best approximates with where I am on these issues. She has bold, realistic ideas. They’re backed with a lot of research and deliberate thought.”

Naset is among the 20% of likely Democratic caucusgoers who describe themselves as “very liberal.” Of that group, 48% back Warren and 20% support Sanders.

Sanders ties Warren among first-time caucusgoers at 22%, and he's second to her in generating support among young people. Twenty-two percent of those younger than 35 say Sanders is their first choice for president, trailing Warren by 5 percentage points.

What does it take to beat Trump?

Iowa’s likely Democratic caucusgoers say that nominating a candidate who has a strong chance of beating President Donald Trump is more important than nominating someone who shares their positions on major issues.

Sixty-three percent say defeating Trump is more important, and 31% say it’s more important to find someone who aligns with them on the issues. Six percent are unsure.

But what does electability look like to likely Democratic caucusgoers?

Asked which of two phrases better fits their definition of the more electable candidate, 74% choose a candidate who can excite new voters and get them to show up, compared to 16% who say it's someone who excites the Democratic base.

Sixty-three percent say a candidate who takes positions seeking to find common ground with Republicans is more electable than someone who takes positions moving the country to the left (28%).

Fifty-seven percent say a candidate who represents a new generation of leadership is more electable than someone who has a long history of serving in government (28%).

And when it comes to dealing with Trump, 54% say the candidate who will “take the high road” is more electable than someone who will “get in the mud as needed” to take him on (35%).

“It’s very hard not to get down in the mud with him. He just kind of brings that out in people,” said J’Andrea Gibney, an 83-year-old poll respondent and Maynard resident. “But you’ve got to take the high road — you can’t be on his level or you’re no better than he is.”

Gibney is among the 59% of likely caucusogers who believe government will return to the way it was if Trump is removed from office in 2020. Majorities of every demographic group agree.

But 30% say they believe Trump’s presidency has permanently changed the way American government works.

The 1-percenters and less

Three candidates are polling at 1%: Montana Gov. Steve Bullock, former U.S. housing secretary Julián Castro and former U.S. Rep. John Delaney of Maryland.

Two candidates — author and activist Marianne Williamson and U.S. Sen. Michael Bennet of Colorado — are polling at 0%, when accounting for rounding.

Three candidates had not a single person name them as their first choice for president: New York City Mayor Bill de Blasio, who ended his campaign Friday, after polling had concluded; U.S. Rep. Tim Ryan of Ohio; and former U.S. Rep. Joe Sestak of Pennsylvania.

Not a single person named de Blasio as either their first or second choice for president in three rounds of Register polling.

“This is what lack of traction looks like in absolute terms,” Selzer said of de Blasio’s numbers.

Among those candidates polling at 1% or below, Castro has the largest universe of people who are considering him in some capacity: 1% say he is their first choice, another 1% say he is their second choice and 20% say they are actively considering him, for a total of 22%.

But as he's become better known (71% can now rate their feelings toward him compared to 47% who could do so in June), Castro's unfavorability rating has nearly tripled. It's risen from 13% in June to 36% today.

The data also suggest that Castro's performance in the Democratic debate earlier this month did him no favors with Iowa Democratic caucusgoers. On the Texas debate stage, Castro appeared to attack Biden's age, asking repeatedly whether the vice president had forgotten what he had said minutes earlier.

See all of our latest Iowa Poll results:

Fifty-four percent of those who say they watched all of that debate view Castro unfavorably. He is viewed unfavorably by 23% of those who watched none of it.

Delaney is the only other lower-polling candidate to crack double digits when looking at the full universe of people considering him in some way. However, that number has shrunk to 10% from 18% since June.

“Most of them have come to Iowa at least once — some of them many times,” Selzer said. “They’ve hired staff. They’ve made an investment. And if you’ve got people who are getting numbers above 50% and you’re not getting 10%, you have to either really up your game or consider the alternative.”

But the caucus field typically doesn’t crystallize until very late, and there is still opportunity for momentum, she said.

The top three candidates — Warren, Biden and Sanders — account for just over half of first-choice votes, totaling 53%. There are now 15 candidates vying for 47% of the remaining electorate.

“Those votes could start to coalesce around one of the also-rans and quite easily pop another candidate into double-digits as a contender,” Selzer said.

Des Moines Register reporters Kim Norvell and Katie Akin contributed to this report.

Brianne Pfannenstiel is Chief Politics Reporter for the Register. Reach her at bpfann@dmreg.com or 515-284-8244. Follow her on Twitter at @brianneDMR.

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​​​​​​​ About the poll

The Iowa Poll, conducted September 14-18, 2019, for The Des Moines Register, CNN and Mediacom by Selzer & Co. of Des Moines, is based on telephone interviews with 602 registered voters in Iowa who say they will definitely or probably attend the 2020 Democratic caucuses.

Interviewers with Quantel Research contacted 3,510 randomly selected active voters from the Iowa secretary of state’s voter registration list by telephone. The sample was supplemented with additional phone number lookups. Interviews were administered in English. Responses for all contacts were adjusted by age, sex and congressional district to reflect their proportions among active voters in the list.

Questions based on the sample of 602 voters likely to attend the 2020 Iowa Democratic caucuses have a maximum margin of error of plus or minus 4.0 percentage points. This means that if this survey were repeated using the same questions and the same methodology, 19 times out of 20, the findings would not vary from the true population value by more than plus or minus 4.0 percentage points. Results based on smaller samples of respondents — such as by gender or age — have a larger margin of error.

Republishing the copyright Iowa Poll without credit to The Des Moines Register, CNN, and Mediacom is prohibited.