Turnout will tell the tale of the Iowa Democratic caucuses, where Barack Obama's theme of a fresh start in the nation's politics is resonating strongly against the bulwarks of Hillary Clinton's campaign -- strength, experience and electability.
Likely caucus-goers are increasingly polarized between these two themes. Obama's enlarged his already sizable lead among those looking mainly for new ideas and a new direction. But Clinton's gained among those focused on strength and experience, and has eased some of her recent negatives on forthrightness and empathy.
Clinton does better with voters who've definitely made up their minds, while Obama is stronger with changeable voters -- still a third of the electorate. He may have more work to do to close the sale in the Iowa campaign's final weeks.
But Clinton has an equal challenge, motivating turnout; she's weaker, and Obama is stronger, among those who say they're absolutely certain to show up on caucus day. John Edwards, while trailing overall, would also benefit from low turnout by newcomers.
Currently, among likely Democratic caucus-goers in this ABC News/Washington Post poll, 33 percent support Obama, 29 percent Clinton and 20 percent Edwards, with single-digit support for the other Democratic candidates. That's similar to the 30-26-22 percent division in the last ABC/Post poll in Iowa a month ago.
Applying tighter turnout scenarios can produce anything from a 10-point Obama lead to a 6-point Clinton edge -- evidence of the still-unsettled nature of this contest, two weeks before Iowans gather and caucus. And not only do 33 percent say there's a chance they yet may change their minds, nearly one in five say there's a "good chance" they'll do so.
Another factor is the Iowa Democratic Party's "viability" rule, in which, generally, candidates who garner less than 15 percent support in the first round of caucusing are dropped, and the contest continues without them. In this poll, when supporters of single-digit candidates are reallocated to their second choice among the top three, Obama goes to a lead, with 37 percent support; Clinton has 31 percent, Edwards 26 percent.
IDEAS and ELECTABILITY -- Fifty-six percent of likely caucus-goers are looking mainly for "a new direction and new ideas," the root of Obama's support. He's backed by 50 percent of these voters, swamping Clinton by 3-1. But she comes back among those focused on "strength and experience," with 49 percent support to Obama's 8 percent.
The polarization between these groups has increased: Clinton's gained 11 points since last month among "strength and experience" voters, while Obama's gained 7 points among those focused on new ideas.
Obama's made notable gains elsewhere. For the first time he runs about evenly with Clinton in Iowa on electability: Thirty-five percent pick her as the candidate with the best chance to win in November, but 33 percent pick Obama -- an 8-point gain for him from last month. He's also battled to an even race with Clinton as the candidate who's campaigned hardest in Iowa, a hard-won attribute in a state accustomed to retail politics.