For the two weeks leading up to a formal announcement Monday, Rep. Michele Bachmann’s presidential campaign has been measured and competent, with the candidate deftly spinning her personal and professional histories into a relatable tale of American industriousness.

The surprise is that Bachmann, who a Fox News host suggest Sunday may be “a flake,” has quickly become one of the more sure-footed candidates in the race for the Republican nomination. She has built on momentum generated in a widely praised debate performance and has sent a jolt of energy through a GOP electorate that has been hungry for someone to be excited about.

“I want this moment to serve as a reminder of the best of who we are as a nation, and of what our values are, and what it is that makes America great,” the Minnesota congresswoman said Monday in a speech officially beginning her campaign here in the town of her birth.

By turning in a savvy performance at a June 13 candidate debate, and tying for first in a recent Des Moines Register poll with front-runner Mitt Romney, Bachmann has forced voters, strategists and her rivals in the race to take her seriously.

If she can sustain her momentum, she could scramble the Republican field, at least in Iowa. She is poised to eclipse former Minnesota governor Tim Pawlenty, who has been organizing in Iowa for a year but fared poorly in the poll. And as she solidifies support among Christian conservatives and tea party activists, she could make it difficult for prospective candidates such as Texas Gov. Rick Perry and former vice presidential nominee Sarah Palin to enter the fray.

Despite her strong start, Bachmann faces considerable challenges. She will have to prove that she is more than a conservative firebrand and that she can appeal to broad swaths of voters. She will have to show that she can build a campaign beyond Iowa, where her roots and the Christian conservative base form a natural constituency for her. And she will have to demonstrate that she has what it takes to be a viable opponent to President Obama — the top concern for many Republican voters.

“Michele has an issue with her lack of experience that she has to overcome,” said Steve Deace, a conservative former radio talk show host who was influential in the GOP caucuses in Iowa in 2008.

Although Bachmann hits all the right socially and fiscally conservative talking points, Deace said, “we want to see that she has good staff. That she shows up on time for events. That the campaign doesn’t miss opportunities to capitalize. And if she can prove that beyond being a conservative ideologue she can do the job of commander in chief, she can do just fine.”

The third-term congresswoman with few legislative accomplishments to speak of is seeking to accomplish the unprecedented. Not since James A. Garfield in 1880 has a sitting member of the House won the White House. Never has a woman.

In beginning her campaign Monday, Bachmann related her own history — growing up in a politically mixed family of modest means, becoming an education activist in Minnesota and eventually being elected to Congress.

She accused Obama of favoring government intervention over American ingenuity and independence, pointing to his health-care overhaul as a prime example. She said that the country should “declare independence from a government that has gotten too big and spends too much and has taken away too many of our liberties.”

The Obama campaign issued a statement Monday after Bachmann’s speech — something it has not done for every candidate — saying that her “policies would erode the path to prosperity for middle-class families.”

Bachmann has managed to strike a delicate balance by moderating her tone without moderating her views. In her speech Monday, she made clear that she is conservative on social issues, fiscal issues and national security and that she is a proud supporter of the tea party. But she also sought to reach out to Democrats.

“Our problems don’t have an identity of party; they were problems that were created by both parties,” she said.

Although she lacks many of the establishment connections that are helping other presidential hopefuls raise money, Bachmann is prodigious in her own un­or­tho­dox way. She raised $13.5 million last year — more than any other House member — much of it from small donors who know her from her cable television appearances.

She has also managed to avoid most of the mistakes and hyperbole for which she has been known. She once characterized the Obama administration as a “gangster government,” compared the mounting debt crisis to the Holocaust and earlier this year claimed that the first shots of the Revolutionary War were fired in New Hampshire instead of Massachusetts.

“If in fact that conduct can sustain itself, and we continue to see that side of her, she is going to be a player,” said J. Warren Tompkins, a GOP strategist in South Carolina, where Bachmann will hold a series of events starting Tuesday night.

She slipped up Monday, however, when she told Fox News that she was proud to share a birthplace with actor John Wayne. It was actually John Wayne Gacy, the serial killer, who lived in Waterloo for a time.

On Fox News Sunday, Bachmann was grilled by host Chris Wallace about apparent inconsistencies in her legislative and personal background. His final question of the interview was: “Are you a flake?”

“I think that would be insulting to say something like that because I’m a serious person,” Bachmann shot back. Wallace issued a video apology to Bachmann on Monday, saying he did a poor job of raising a common criticism of the candidate.

What few dispute is that Bachmann knows how to rev up a conservative crowd. On Sunday night, she received rock star treatment at a rally at an old ballroom, where she told nostalgic stories of walking to school as a child here and eating mayonnaise-and-lettuce sandwiches with her brother. She lingered long afterward, signing autographs, snapping pictures and mingling at a media reception for 45 minutes..

“She’s awesome. There’s no words to describe her,” said Susan Nelsen, 60, a teacher from Waterloo. “She’s what it’s going to take to clean up the White House.”

But even among the adoring crowds were skeptics. Jeff Engel, 48, said that he likes Bachmann and might back her, but added that is also considering Romney because he may be more electable. “All I truly care about,” he said, “is getting someone who can beat Obama.”