How each Democrat rates in new Iowa Poll

1. HILLARY CLINTON, former secretary of state

Eighty-four percent of likely Democratic caucusgoers view her favorably, while just 15 percent have negative feelings, the Des Moines Register/Bloomberg Politics Iowa Poll shows. She's the first choice for 56 percent of likely caucusgoers.

Clinton enjoys nearly universal recognition, and she's the favorite even among poll respondents who say they'd like to see an "anti-establishment" candidate become president.

The benefits of such a dominant position come in campaign organizing and fundraising, said Democratic strategist Jeff Link. At this phase, a campaign is less focused on polling and more focused on developing a message and a rationale for running, he said.

"The main thing that any candidate needs to do in these early stages is figure out why they're running and what they'd want to do if elected," Link said.

2. ELIZABETH WARREN, U.S. senator from Massachusetts

Fifty-eight percent of likely Democratic caucusgoers view her favorably, compared with 11 percent who have negative feelings and 31 percent who are unsure. She's the first choice for 16 percent of likely caucusgoers.

A draft effort by liberal groups appears to be raising Warren's profile, and the people who are discovering Warren generally like her, but her seriousness as a presidential candidate remains unclear. She has consistently said she is not a candidate for president, even as she's been coy about whether that could change.

If she did get into the race, Warren would be a viable competitor in Iowa, Link said.

"She would make for a competitive race," he said. "She would push and challenge Secretary Clinton organizationally with the grass-roots."

3. JOE BIDEN, vice president

Biden is viewed favorably by 78 percent of likely caucus attendees and unfavorably by 20 percent. He's the first choice for 9 percent of likely caucusgoers.

Like Clinton, Biden is extremely well-known in Iowa, the result of serving six years as vice president and running two previous presidential campaigns here. That alone gives him an edge on many of the potential candidates in the field.

It's unclear whether Biden will run or if he would challenge Clinton, but he has made a couple of trips to Iowa in recent months, including one just days after Clinton reintroduced herself to Iowans at the Harkin Steak Fry last September.

The challenge for Biden will be establishing a niche in a field potentially dominated by Clinton in the middle and Warren on the left, said University of Northern Iowa political scientist Chris Larimer.

"For him to have any kind of significant impact, the two in front of him would have to not be in the race," Larimer said. "That's the only way he gets any ideological space or momentum in the caucuses."

4. BERNIE SANDERS, U.S. senator from Vermont

Not many likely caucusgoers know Sanders well enough to form an opinion: 51 percent say they're not sure about him, while 37 percent view him favorably.

Twelve percent have negative feelings about him. He's the top choice of 5 percent of likely caucusgoers.

Out of all the candidates, Sanders has been the most active in Iowa over the last several months, speaking at Democratic and progressive events and meeting privately with labor leaders and others in the party's liberal base. Those efforts haven't translated to popular support yet, but could lay a foundation should he formally announce a campaign.

More likely, though, is that Sanders, who identifies himself as a Democratic socialist, is trying to widen the conversation on liberal priorities such as income inequality, financial regulation and the social safety net, Larimer said.

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"He's really just trying to shape the conversation, trying to shape the agenda and trying to get certain issues talked about," Larimer said. "If Elizabeth Warren doesn't run, Bernie Sanders is that one candidate who can get attention on some of those issues."

5. JIM WEBB, former U.S. senator from Virginia

Webb is largely unknown to likely Democratic caucusgoers, with 68 percent saying they're unsure of their opinion about him. Twenty-one percent have a positive opinion. Three percent call him their top choice for the caucuses.

6. MARTIN O'MALLEY, former governor of Maryland

Despite a handful of visits to Iowa through the 2014 campaign season, O'Malley is a virtually stranger to likely caucus attendees.

Seventy-eight percent say they aren't sure about him and just 13 percent view him favorably. Just 1 percent of Iowa Poll respondents call him their first choice for the caucuses.