WASHINGTON - On the eve of the Iowa caucuses that could all but doom her flagging bid for the presidency, Michele Bachmann's closing argument can be summed up in two words: Iron Lady.

In a last-ditch bid to catch the leaders, the Minnesota Republican has worked former British Prime Minister Margaret Thatcher into her latest Iowa stump speech, making the comparison to play up her resiliency, but also the chief difference between her and the rest of the GOP field.

"We need an American Iron Lady," she said at her Iowa headquarters over the weekend. "We need an American who is strong, and a female."

Bachmann's transition from describing her "titanium spine" to comparing herself to Britain's iconic "Iron Lady" marks the congresswoman's closest flirtation with gender politics, something she has largely avoided in her long-shot quest for the White House.

But it also raises questions about a possible gender barrier she could face in the closing days of Tuesday's contest in Iowa, where she is targeting some of the most socially conservative voters in the nation.

Until now, the issue hasn't been an explicit part of the GOP primary conversation, where the diminutive 55-year-old politician has been the only woman on the stage.

"As it gets closer to the caucuses, Iowans are starting to look more closely at who they think could beat Barack Obama," said Dianne Bystrom, an expert on women in politics at Iowa State University. "So they start looking more at electability, and I do think it hurts that Michele Bachmann is a woman."

Bachmann's critics argue that her long slide in the polls has more to do with her frequent misstatements and the appearance of turmoil within her campaign staff than her gender. But there's little question that women seeking high office still face subtle gender stereotypes.

"I think there's a gender barrier for any woman in politics right now, whether it be on the right or the left," said Winston Frost, a government professor at Oral Roberts University, where he and Bachmann attended law school together. "Look what happened to Hillary Clinton in the last election."

Iowa is famously where Clinton's 2008 presidential campaign first stumbled. The state also holds the distinction -- along with Mississippi -- of never having elected a woman to Congress or the office of governor.

While Iowa voters are politically progressive in many respects, Bystrom said, "our culture here isn't necessarily the most amenable to women." In part, she attributes that to an electorate that skews older, rural and more "traditional" in its social orientation.

'Iowans are up for it'

Bachmann, for her part, dismisses the idea that Iowans won't send a woman to the nation's highest office.

"Iowa's already shown that the United States is ready for a female president, because I won the Iowa straw poll," Bachmann said during her just-concluded tour of the state's 99 counties. "That was a huge victory this last August, and it demonstrated that Iowans are up for it."

More recently, she has combined Thatcher's tough "the lady's not for turning" image with an appeal to the pioneering spirit of her native state. "I think a lot of you men know about strong Iowa women," Bachmann told supporters Saturday at her headquarters in Urbandale. "A few of you are married to strong Iowa women. That's what I intend to be. I am an Iowa woman, and I intend to be ... America's Margaret Thatcher."

The theme has been echoed by Bachmann's supporters across the state. Tamara Scott, Iowa political director for Concerned Women for America, appeared at a Bachmann rally in Waukee last week and called her "the Margaret Thatcher of our time."

Former Iowa legislator Danny Carroll, warming up another Bachmann crowd in Indianola last week, announced, "Perhaps it's time to put a woman in the White House to straighten out the mess we're in."

'It means respect'

As an evangelical Christian, Bachmann has faced questions about her view of the role of women in society. At a debate in Ames in August, she was questioned about her past statements on the submissive role of wives. "It means respect," she said. "I respect my husband. ... He respects me as his wife."

While Bachmann has benefitted from strong support among fellow evangelicals, her candidacy has given some of them pause. Two of Iowa's leading evangelical leaders, the Rev. Albert Calaway and the Rev. Cary Gordon, recently endorsed Christian conservative Rick Santorum. They suggested that in order to unify the evangelical vote in the state, Bachmann could serve as Santorum's running mate.

Bachmann has ruled out that prospect. Meanwhile, she has turned to the Thatcher pitch to reinforce her image as a strong woman who won't back down from her conservative principles. Tuesday's caucuses will show whether the message gained Bachmann new traction.

Julie Thompson, an Urbandale homemaker who calls herself a Christian conservative, said she has been persuaded.

"I'm hoping it will resonate with women," said Thompson. She decided to support Bachmann last week because of "her consistency."

Then there are social conservatives like Faith Ward, a special-education worker from Ackworth who went to a Bachmann rally last week. She remains unsure whether she'll vote for Santorum, Texas Gov. Rick Perry or Bachmann.

"I haven't heard her say anything against what I believe," Ward said of Bachmann. "I'm just a little on the fence about having a woman as president."

Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.