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A slide in favorable feelings toward U.S. Sen. Bernie Sanders has accompanied his slide into third place in the latest Des Moines Register/CNN/Mediacom Iowa Poll.

The net favorable rating for Sanders — a combination of likely Democratic caucusgoers who report feeling very or mostly favorable toward the senator from Vermont — has dropped from a high of 74% last December to 58% in September. His net unfavorable rating, combining those whose feelings are mostly or very unfavorable — rose nearly as much in that time, going from 22% to 36%.

Both ratings were relatively stable in Iowa Polls before September. The biggest shifts come from the portion of likely caucusgoers who report their feelings as very favorable toward him — a drop from 43% in December to 26% now.

Sanders has the highest unfavorable rating of the five top-polling candidates. In the latest Iowa Poll, Elizabeth Warren leads in first-choice preferences, followed by Joe Biden, Sanders, Pete Buttigieg and Kamala Harris.

Warren also outperforms Sanders among those who caucused for him in 2016. He’s the first choice for 25% of people who say they backed him then, while Warren is the top pick for 32%. She also draws in 22% of Hillary Clinton’s 2016 caucusgoers, while Sanders draws none of Clinton's former supporters.

“There’s not a lot of good news for Bernie Sanders in this poll,” pollster J. Ann Selzer said. She also noted the field is still very fluid. He's campaigning with the same message as he did in 2016 but is not holding a plurality of the people who joined his call before, she said.

The poll of 602 likely Democratic caucusgoers was conducted Sept. 14-18 by Selzer & Co. It has a margin of error of plus or minus 4 percentage points.

The results are not all doom and gloom for Sanders, however. Nearly half of respondents who pick Sanders as their first choice for president describe themselves as "extremely enthusiastic" about their candidate. For Warren, that figure is 32%.

He ties her as the top candidate for likely first-time caucusgoers, with 22% — a key metric for a campaign targeting people previously disengaged from politics.

Poll respondent and self-proclaimed “full-hearted” Sanders supporter Andrew Long said Sanders has different expectations this time after nearly winning Iowa and going from underdog to contender in 2016.

Long, 41, of Ankeny, was a precinct captain for Sanders in 2016, and said his enthusiasm for Sanders has only grown. He's drawn to his policies, he said, before rattling off Sanders’ proposals for universal health care, free tuition at public colleges and universities and a “Green New Deal.”

"A person like Sen. Sanders, who is able to articulate in a cogent fashion issues facing real Americans, is the way to win the presidency,” Long said.

Nick Coltrain is a politics and data reporter for the Register. Reach him at ncoltrain@registermedia.com or at 515-284-8361. Your subscription makes work like this possible. Subscribe today at DesMoinesRegister.com/Deal.​​​​​​​

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About the poll

The Iowa Poll, conducted Sept. 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.