Fresh off a formidable showing in an Iowa preference poll of 2012 Republican presidential candidates, Rep. Michele Bachmann on Sunday said that as president she would offer a federal constitutional amendment to list marriage as solely between a man and a woman.

However, the Minnesota congresswoman said it's also up to the states to decide whether they permit same-sex marriage.

Bachmann, who has staked out much of the social conservative ground in the GOP primary race, was threading a thin needle in explaining that her views are not inconsistent on gay marriage. She was speaking after New York's Legislature this weekend approved same-sex marriage, making it the sixth state to allow it.

"The states have the right to pass the laws they want to," Bachmann told "Fox News Sunday," adding that such an issue should really be on the ballot so that voters can decide whether gay marriage should be the law of the land.

"Every time it's going on the ballot, the people have decided to keep the traditional definition," she said. "After all, the family is the fundamental unit of government."

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But Bachmann added that it's not a contradiction to pursue a federal constitutional amendment that would trump state law, and if she were president she would do so. A constitutional amendment would require a two-thirds vote of Congress and ratification by three-quarters of the states.

"It's a high hurdle. We only have 27 amendments to the federal Constitution," Bachmann acknowledged.

The last place, it should be decided, however, is in the courts, she added.

Bachmann is formally declaring her candidacy Monday in Waterloo, Iowa, where she was born. She said her native ties give her a distinct advantage in the nation's socially conservative and first primary polling state.

Bachmann, who came a close second to Mitt Romney in a much anticipated poll released by the Des Moines Register on Saturday, refused to say whether she thinks the front-runner is a flip-flopper, but argued he "has a history of varying his position" on the issue of abortion.

She said the Republican Party needs a candidate who represents the platform of the party, which is pro-life. And Romney should have signed a pro-life pledge when given the opportunity.

"Mitt Romney has to say what he is, but I have to say if he's saying now that he is pro-life, this is a tremendous opportunity to sign the Susan B. Anthony List pledge, and I think it's disappointing he didn't," Bachmann said. The SBA List is an organization that tries to get pro-life candidates elected.

As for federal spending, the congresswoman, who claimed that as president, her "first and singular" focus will be on turning around the economy, said she wasn't playing fast and loose with federal money that benefited workers at a counseling clinic she and her husband own, or with subsidies to a farm owner by her father-in-law. The clinic received $30,000 and the farm got $260,000.

"The money that went to the clinic was actually training money for employees. The clinic did not get the money, and my husband and I didn't get the money either," she said, adding that in reality the clinic suffered from the training sessions because staff were away from their duties in order to go to the training.

"It helped the employees," she said.

As for the farm, the Los Angeles Times reported Sunday that it received $260,000 mostly from corn and dairy subsidies between 1995 and 2008. Even though the congresswoman's father-in-law died in May 2009, she remains a partner in it. She reported in her financial disclosures receiving between $32,503 and $105,000 between 2006 and 2009.

Bachmann, who has publicly opposed federal farm payments and voted against the 2008 farm bill, reportedly opposed the "outrageous pork and subsidies" in the five-year, $307 billion package.

But Bachmann told "Fox News Sunday" she and her husband have "never gotten a  penny of money from the farm."

Bachmann also said that she doesn't apologize for taking $60 million in state earmarks for Minnesota during her first term in Congress, which was used to build roads and bridges, but she has since signed a pledge to take no earmarks.