"There are four campaigns really working and organizing for the straw poll: Pawlenty, Bachmann, Paul, and Santorum," said Craig Robinson of the Iowa Republican.
Every one has "a different strategy," he continued. "Pawlenty has the traditional organization apparatus to fill buses and get people to Ames, but they're sticking close to a 60-mile radius of Ames when they're campaigning. Santorum, though, is campaigning all across the state and actually getting traction in these border communities.
"Paul will have the most passionate supporters there," added Robinson. "He turned out 1300 people four years ago with little effort and this time around they have a pretty substantial apparatus, so he'll do better."
Bachmann, he said, was "really hurt" with the debt ceiling debate in terms of campaigning. But "she has far more hype and interest. She had a crowd of 60 people in Sioux City the other day and she wasn't even there – she did it by phone from DC. So there's a lot of intensity on her side. She's got to win – if she doesn't win, she's in big trouble."
A top Republican operative in Iowa, speaking on the condition of anonymity, told ABC News, "I think Ron Paul or Tim Pawlenty is going to win this thing, and Bachmann is going to come in a disappointing third. Church groups and home-schoolers have not all coalesced around her campaign like they did for Huckabee last time. And her campaign hasn't figured that out yet. They don't know what kind of trouble they're in. If they don't figure this out in the next 10 days, then I think this could be the beginning of the end for her."
Pawlenty's campaign, the source said, "knows what they're doing." And Paul's approach could resonate with voters because they saw him in Iowa four years ago talking about the nation's debt problem.
"I think that Paul's team has a plan and they're executing it flawlessly," continued the source. "He's got the credibility that even someone like Bachmann does not – because he's been saying this for years and years in some of the same ballrooms he's speaking in right now."
But Bachmann remains the favorite. Touring the state, she's drawn large crowds on a regular basis in recent weeks. And the fact that this year's straw poll is preceded two days earlier by a debate may play to her strengths. Bachmann shined in the debate in New Hampshire earlier this summer, outperforming her rivals and sending her poll numbers soaring.