The result is the first indication of what Iowans think of the field of Republicans competing for the chance to challenge President Barack Obama next fall. But it's hardly predictive of who will win the winter Iowa contest, much less the party nod or the White House.
Rather, Saturday's outcome suggests that Bachmann has a certain level of support and, perhaps even more important, the strongest get-out-the-vote operation and widest volunteer base in a state whose caucuses require those elements.
Texas Rep. Ron Paul finished a close second while former Minnesota Gov. Tim Pawlenty placed a distant third.
"We have a lot more work to do," Pawlenty said, making clear he wasn't dropping out despite a disappointing finish. "We are just beginning and I'm looking forward to a great campaign."
The results of the nonbinding vote, held on the Iowa State University campus, came just hours after Texas Gov. Rick Perry entered the race.
"I full well believe I'm going to win," Perry told South Carolina voters on a conference call before delivering his first speech as a candidate.
"It's time to get America working again," he declared in Charleston, S.C. "America is not broken. Washington, D.C. is broken."
Despite Perry's best efforts to overshadow the day, the epicenter of the presidential contest was in this Midwestern town, where nearly 17,000 Iowans cast ballots during a daylong political festival, a late-summer ritual held every four years.
In speeches throughout the day, candidates scouted for support by assailing Obama and offering themselves as the answer to an America plagued by high unemployment, rising debt and stock market swings.
"We know what America needs. But unfortunately Barack Obama has no clue. He's like a manure spreader in a windstorm," Pawlenty said, adding: "Mr. President, get the government off our backs." That elicited chants of his nickname: "T-Paw! T-Paw! T-Paw!"
Pawlenty had a lot on the line. He's ranked low in polls and was looking to prove he was still a viable candidate. He argued that he was the candidate of results, given his record as Minnesota governor.
Bachmann stressed faith and her Iowa roots - she was born in Waterloo - as well as her opposition to abortion rights and gay marriage. She earned cheers when she declared: "We are going to make Barack Obama a one-term president."
Bachmann, riding high since entering the race earlier this summer, had hoped that a strong finish would give her even more momentum just as Perry looks to infringe on her base of tea party and evangelical support. She invoked God and faith as she stressed what she called her conservative values, saying: "In Iowa, we are social conservatives and we will never be ashamed of being social conservatives."
Paul, with a following among libertarian-leaning voters, wanted a surprise showing that might convince Republicans he was more mainstream than not in his second shot at the GOP nomination. He referenced his fellow Texan's entrance in the race and said he didn't anticipate many of his supporters jumping ship for what he called a "super-establishment candidate."
Former Pennsylvania Sen. Rick Santorum, businessman Herman Cain and former U.S. House Speaker Newt Gingrich of Georgia also were on the ballot. So were GOP front-runner Mitt Romney and former Utah Gov. Jon Huntsman, though they weren't competing in the contest.
Perry and former Alaska Gov. Sarah Palin, who made a splash Friday when she visited the state fair, weren't listed. But their backers planned write-in campaigns that could outpace candidates who have spent months trying to line up supporters to participate.
The straw poll isn't a scientific poll at all; it amounts to a popularity contest and a test of organizational strength.
Poor showings usually force some candidates, mostly those who are not well-known and are struggling to raise money, to abandon their bids. That could happen this year, too.
The straw poll has a mixed record of predicting the outcome of the precinct caucuses.
In 2008, Romney won the straw poll, but the big news was the surprising second-place showing of former Arkansas Gov. Mike Huckabee. Huckabee won the Iowa caucuses, but dropped from the race soon after. Sen. John McCain, who eventually won the nomination, didn't compete in the straw poll and finished in 10th place.