Democrats at a glance

Hillary Clinton

First choice: 37 percent

37 percent Rank in field: First

First Change since May: Down 20 points

Down 20 points Favorability: 77 percent

77 percent Change since May: Down 9 points

Down 9 points Candidate bio

Veteran caucusgoers liked Clinton in 2008, and the pattern is repeating. She leads by 12 percentage points against Bernie Sanders with that group (39 percent to 27 percent).

She also wins among self-described Democrats by 13 points (40 percent to 27 percent). Although Sanders is running for the Democratic nomination, he has been elected to the U.S. House and later the Senate each time as an independent.

A majority of Sanders supporters opt for Clinton as their second choice (54 percent).

If Clinton were to drop out of the race, 51 percent of her supporters would like to see another candidate join the field; 39 percent are satisfied with the current slate.

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Bernie Sanders

First choice: 30 percent

30 percent Rank in field: Second

Second Change since May: Up 14 points

Up 14 points Favorability: 73 percent

73 percent Chance since May: Up 26 points

Up 26 points Candidate bio

Sanders leads Hillary Clinton with first-time caucusgoers (43 percent to 31 percent); independents (45 percent to 24 percent); self-described liberals (42 percent to 37 percent); and in the 3rd District, which stretches across southwestern Iowa, from Des Moines to Council Bluffs (38 percent to 27 percent).

Sanders and Clinton are close in their favorability rating (77 percent view Clinton favorably, 73 percent for Sanders), but 39 percent have a very favorable view of Sanders, compared with 27 percent for Clinton.

Among those who choose him as their first choice, 28 percent have an unfavorable opinion of Clinton.

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Joe Biden

First choice: 14 percent

14 percent Rank in field: Third

Third Change since May: Up 6 points

Up 6 points Favorability: 79 percent

79 percent Change since May: Up 3 points

Slightly more likely caucusgoers view him favorably compared with Hillary Clinton (79 percent to 77 percent), and fewer view him negatively (14 percent to 19 percent).

Among those who choose him as their first choice, 35 percent have an unfavorable opinion of Clinton.

A plurality of Clinton supporters opt for Biden as their second choice (44 percent).

Martin O'Malley

First choice: 3 percent

3 percent Rank in field: Fourth

Fourth Change since May: Up 1 point

Up 1 point Favorability: 33 percent

33 percent Change since May: Up 13 points

Up 13 points Candidate bio

Eight percent of likely caucusgoers pick him as their second choice.

Sixty percent don't know enough about him to form an opinion of him.

Thirty-eight percent think they could support him, but 21 percent believe they never would.

Jim Webb

First choice: 2 percent

2 percent Rank in field: Fifth

Fifth Change since May: No change

No change Favorability: 19 percent

19 percent Change since May: Down 3 points

Down 3 points Candidate bio

One percent select him as their second choice.

Sixty-eight percent don't know enough about him to form an opinion of him.

Thirty-six percent think they could support him, but 26 percent believe they never would, twice as many as in the May Iowa Poll.

Lincoln Chafee

First choice: 1 percent

1 percent Rank in field: Sixth

Sixth Change since May: Not a declared candidate at time of May poll

Not a declared candidate at time of May poll Favorability: 9 percent

9 percent Candidate bio

A single respondent picked him as first choice and two as second choice.

One statistic best sums up his candidacy to date: 80 percent don't know enough about him to form an opinion of him.