Using the backdrop of the Henry Ford museum in Dearborn, Mich., Mitt Romney formally announced his presidential bid Tuesday, emphasizing the need for Washington to pursue "innovation and transformation" in the face of persistent and heady challenges.

"It is time for innovation and transformation in Washington. It is what our country needs. It is what our people deserve," Romney told supporters. "And so ... with the fine people of Michigan before us, and with my sweetheart beside me, I declare my intention to run for President of the United States."

Trying to distinguish himself from other candidates in the race, including top Republican rival, Arizona Sen. John McCain, Romney emphasized that he is not a Washington insider, but also not an untested chief executive.

Click here to read more about the 2008 presidential race at's You Decide center.

"I do not believe Washington can be transformed from within by a lifelong politician. There have been too many deals, too many favors, too many entanglements and too little real world experience managing, guiding, leading," he said.

"I do not believe Washington can be transformed by someone who has never tried doing such a thing before, in any setting, by someone who has never even managed a corner store, let alone the largest enterprise in the world," Romney continued.

But even while the former Massachusetts governor makes his official launch, he faces several challenges, not first of which is that several state representatives who had planned to support Romney are now moving to his rival's camp.

The group of state lawmakers, which had pledged to support Romney in 2008, will announce at a press conference in Lansing that they've switched their support from Romney to McCain.

Three-term state Rep. Judy Emmons said she backed Romney on the word of former House Speaker Craig DeRochem, who will be introducing Romney at the Dearborn event. But Emmons told FOX News on Monday that after researching the candidates on her own, she came to view McCain as the better choice.

Emmons said part of the decision came down to Romney's position on abortion, and a conservative conversion that has plagued Romney since he entered national politics.

McCain's "pro-life record is compelling," Emmons said. "For 20 years, he's been pro-life every step." Romney, on the other hand, has a "consistency issue."

Emmons said she also has respect for McCain's "willingness to be at the forefront of protecting our country from terrorism" and praised him as "fiscally responsible."

Romney is largely acknowledged as the third member of the Republican top tier in the 2008 race, joining McCain and former New York City Mayor Rudy Giuliani. Romney has demonstrated an ability to rally Republicans to his cause — endorsements range from members of ex-Florida Gov Jeb Bush's inner circle to Capitol Hill lawmakers, including former House Speaker Dennis Hastert — and to raise money. He took in more than $6 million on the day he announced his exploratory committee.

But the "consistency issue" is sure to dog Romney throughout his battle for the GOP nomination for president. Romney favored safe, legal abortions until he became governor of Massachusetts, but says he was dissuaded from his abortion-on-demand position by a Harvard stem cell scientist. Afterward, Romney announced his opposition to embryonic stem cell research and later that year vetoed a bill making available Plan B or "morning after" contraception.

In 1994, Romney also has said he'd be a stronger proponent of gay rights than liberal senator Ted Kennedy, who he ran against that year.

Click here to watch the YouTube video of the 1994 Kennedy-Romney debate.

On a separate issue, as a Mormon, Romney could also face resistance from Christian evangelicals, who comprise a sizable and powerful chunk of the Republican Party. A recent FOX News poll showed that 32 percent of voters said they would be less likely to vote for a candidate if he's Mormon. Nine percent said they'd be more likely.

In that same poll, 11 percent said they had a favorable view of Romney while 22 percent said they had an unfavorable view. But 67 percent said they don't know him or enough about him yet to weigh in.

Last week, Romney told FOX News that "anything's fair in politics" but he didn't think his religion would be a hindrance.

"In my view, the people of America want a person of faith to lead the country. I believe in God. I believe that — that all of His children are — are around us, in the various nations and in this great nation. ... And I believe that if people want to understand the nature of my faith, they can look at my wife and me and our family. They can see that our faith has made us better people, better Americans," he said.

In his announcement, Romney sought to head off questions about where he stands and appeal to conservative voters.

"It has been said that a person is defined by what he loves and by what he believes and by what he dreams. I love America and I believe in the people of America. I believe in God and I believe that every person in this great country, and every person on this grand planet, is a child of God," Romney said.

"I believe the family is the foundation of America — and that we must fight to protect and strengthen it. I believe in the sanctity of human life. I believe that people and their elected representatives should make our laws, not unelected judges. I believe we are overtaxed and government is overfed ... I believe that homeland security begins with securing our borders. I believe the best days of this country are ahead of us," he said.

SPEAKOUT!! Will Romney's religion pose a problem in his presidential bid?

Romney and McCain have been going toe-to-toe behind the scenes for months. McCain has announced a slew of endorsement in Romney's home state of Michigan, and the campaign held its first voter rally in Massachusetts. Romney countered by announcing supporters from McCain's home state of Arizona the same day.

With fellow top-tier candidate Rudy Giuliani lagging behind in campaign organization, McCain and Romney have also been battling it out for supporters on Capitol Hill and in the key primary states of Florida and South Carolina.

Romney did misstep among some in the Jewish community, however, by choosing Ford museum for the presidential announcement. Ford, a well-known anti-Semite, was bestowed the Grand Service Cross of the Supreme Order of the German Eagle by Adolph Hitler.

Romney's father, George, is a former automobile executive and three term governor of the state. In the face of criticism Monday, his campaign said the announcement would go on as scheduled.

FOX News' Aaron Bruns and Jake Gibson contributed to this report.