There are good reasons Edwards is seen as having campaigned more in the state: He ran there in 2004, finishing a creditable second to John Kerry and leaving himself a prebuilt campaign organization. He was back in Iowa earlier than his top competitors this cycle. According to a Washington Post count, he's held 69 events in Iowa this year, compared with 60 by Obama and 41 by Clinton.
Edwards, by extension, has seen his message resonate better in Iowa. Among people who care more about "a new direction and new ideas" than about strong leadership, 31 percent support Edwards in Iowa, compared with 10 percent nationally.
Clinton's supported by just 15 percent of "new direction" voters in Iowa, versus 39 percent nationally. This remains a key group for Obama; he gets 37 percent from "new direction" voters in Iowa (about the same as nationally). By contrast, among those more focused on strength and experience, Obama gets far less support, just 14 percent.
Strength and experience are Clinton's attributes. She swamps her opponents, especially on experience; 50 percent pick her as having the best background for the job, versus just 7 percent for Obama and 15 percent for Edwards. But she lags both of them in honesty and trustworthiness as well as likability. And while Clinton nationally leads in her party by wide margins in understanding people's problems and in being "closest to you on the issues," Iowans divide much more closely on these among all three top candidates.
Clinton's supported by 31 percent of women in Iowa, compared with 21 percent of men, a gender gap not unlike the national figure; and, as nationally, she's stronger among lower-income voters. (Women also are 18 points more likely to be "very satisfied" with their choice of candidates, 61 percent to 43 percent.) But it's Obama who shows the most difference among population groups. He's got 38 percent support from likely caucus-goers under age 50 -- leading Clinton and Edwards in this group -- but just 15 percent support from senior citizens, a group in which Edwards leads.
Young people are notoriously hard to turn out, but Obama also leads among a more reliable voting group, highly educated adults. He's got 35 percent support from likely caucus-goers who have postgraduate degrees, compared with 19 percent among those who haven't gone beyond high school.
Obama also does better among Iowans who say it'll be their first caucus -- 34 percent of them support him -- than among those who say they've attended previously, 23 percent. The question again is to what extent newcomers do attend. (In the 2004 Iowa entrance poll, 55 percent said it was their first caucus, but that's partly because there hadn't been a highly contested Iowa caucus since 1988. In this poll, 31 percent say it'll be their first caucus.)
There are no significant differences among the top candidates in preferences among voters from union households, a sizable group in Iowa -- 22 percent of likely caucus-goers in this survey.
Looking at candidates' attributes underscores their liabilities as well as their strengths. In the most striking example, only a quarter of Obama's own supporters say he has the best experience in the field, as do just 45 percent of Edwards' supporters -- compared with 89 percent of Clinton's. Indeed, Obama's own supporters are almost twice as likely to say Clinton has the best experience as to say Obama does.