Washington (CNN) -- Rep. Michele Bachmann boasted of having a "titanium spine" in an interview broadcast Sunday, the day before she formally enters the race for the Republican presidential nomination in 2012.
However, Bachmann had some difficulty in clarifying her stance on key issues and explaining federal funding that benefited her family in the interview on "Fox News Sunday" and another one with the CBS program "Face the Nation."
"I have a titanium spine for doing what we need to do" to get the country turned around, Bachmann told Fox, later challenging a question about whether past misstatements showed she was "flaky" by saying: "I think that was insulting to say something like that, because I'm a serious person."
The 55-year-old Tea Party favorite from Minnesota has bolted into leading contention among Republican candidates so far after a strong performance earlier this month in a New Hampshire GOP debate.
She will announce her candidacy on Monday in Iowa, the state where she was born and an important first destination in presidential campaigning.
"I have a distinct advantage there, I think," Bachmann said of Iowa.
She listed her accomplishments as a tax lawyer, legislator and mother, and cited her sincerity as a major strength in comparison to the other leading GOP contender early in the campaign -- former Massachusetts Gov. Mitt Romney.
"What people know about me is I do what I say and I say what I mean," Bachmann said on Fox, calling herself a "fighter" and a "common-sense voice." "I think people recognize I'm very sincere in what I say."
However, she stopped short of calling Romney insincere, though she noted he has changed positions in the past on key issues including abortion.
Bachmann, a deficit hawk who backs deep spending cuts to balance the federal budget, adopted a defensive posture when asked about a Los Angeles Times report Sunday on federal money that benefited her family -- including nearly $30,000 for a counseling clinic operated by her husband and almost $260,000 for a family farm.
The money didn't directly benefit her family, she explained, saying the $30,000 was for training employees and the farm that got the $260,000 was owned by her father-in-law, so she and her husband didn't get any of it.
Asked about another roiling social issue -- gay marriage -- Bachmann said she supported both the right of states to pass laws on the matter and the superseding authority of a federal constitutional amendment on the issue.
New York's state legislature and governor have the right under the Tenth Amendment to pass the law legalizing gay marriage, which happened Friday, Bachmann said.
She also backs a federal constitutional amendment that would define marriage as between a man and a woman, saying that would decide the issue once and for all.
In the end, Bachmann said, it would be better to settle the matter with citizens voting on a constitutional amendment rather than Supreme Court judges issuing a decision.
Asked on CBS whether she believes homosexuality is a choice, Bachmann said it was up to individuals to make their own decision and that she wasn't judging anyone on the issue.
She described herself as a Christian who gave her heart to Jesus Christ at age 15 and now gets guidance in her life and political career through prayer. Her doctrine is rigid conservatism on economic and social issues, and she responds to most policy questions -- especially on the economy with withering criticism of President Barack Obama.
"The president doesn't seem to have an understanding of how the economy works," Bachmann said on CBS. "It doesn't seem he has a basic understanding of how do the job of president of the United States."
She challenged the contention by the White House, Treasury Secretary Tim Geithner and economic analysts that failing to raise the federal debt ceiling by August 2 would cause a negative market reaction.
"It is scare tactics," Bachmann said of such warnings, adding that the government takes in plenty of money to pay the interest it owes on federal debt and avoid default. In that case, she conceded, other spending such as funding the military would have to be cut.
"It would be very tough love," she conceded, adding that she had no intention of voting to raise the debt ceiling at this time. If president, Bachmann said, she would cut corporate taxes in several ways in order to spur job creation, but she stopped short of endorsing a call from her past to eliminate the minimum wage.
Bachmann has a history of statements that media fact checkers such as PolitiFact.com have revealed to be untrue, including false claims that Obama's trip to India cost taxpayers $200 million a day and that Obama had only issued one drilling permit since taking office. Asked about that record, she responded: "I haven't misled people at all."
As a newcomer to presidential politics, Bachmann wasn't asked Sunday whether she would accept an invitation to run for vice president if defeated by another Republican candidate.
She may have inadvertently tipped her hand on Fox, though, when she accidentally referred to Romney as "President Romney" before correcting herself.