(CNN) -- Former Massachusetts Gov. Mitt Romney announced Thursday that he is in the race for the 2012 Republican presidential nomination.
Romney, who ran for the nomination in 2008, is the sixth Republican to formally announce a campaign. Here are five things to know about him:
A less stiff Mitt? During the 2008 campaign, Jon Stewart called him "Captain Buzz-kill" and described him as looking like "everyone who has ever fired your dad." David Letterman said he looked like the photo that comes with the frame.
Romney is trying to change that this time around -- he's making appearances without a tie. A Twitpic sent on Memorial Day showed him posing with his family, wearing a polo shirt with his hair slightly mussed.
He even attempted a well-publicized prank on President Obama last week, sending some leftover slices of pizza from a visit to Obama's hometown of Chicago to the White House.
We're not sure what the prank was, though -- the pizza was already paid for.
Is health an issue? Not Romney's physical health, but the universal health care law he got passed in Massachusetts when he was governor there from 2003 to 2007. Obama has already been using the issue against Romney, saying he got an "assist" from Romney in getting Obama's health care law passed last year.
Republican rivals have also been taking shots at Romney's history with universal health care and more are sure to come during the campaign.
In a speech last month at the University of Michigan, Romney tried to get ahead of the issue by saying that the difference between the Massachusetts plan and Obama's was that his "experiment" in Massachusetts was never designed to be "forced" upon the country like Obama's.
A Mormon in the White House? Romney would be the country's first Mormon president, but his faith is something he'll have to overcome among Republican voters: A Pew poll before the 2008 campaign found that one in four Americans would be less inclined to vote for a Mormon candidate. A Gallup survey around the same time found that 18% of Republicans said they would not vote for a Mormon for president.
Romney doesn't see it that way, telling CNN's Piers Morgan that, "My experience so far both in Massachusetts running as a Mormon guy in a state that's overwhelmingly of other faiths is it didn't seem to get in my way there. Most people in the country recognize that in fact the nation itself was founded on the principle of religious tolerance and freedom. We respect other people's beliefs and in a lot of cases people who honor faith and try and be true to it."
What do voters think? Romney got the second-most number of votes in the 2008 Republican primary before conceding to nominee Sen. John McCain.
He has placed at or near the top of most Republican presidential preference polls in the run-up to the election, but most experts say polls this early in the cycle are more about name recognition than whether voters agree with a candidate's positions on issues.
In Palin's shadow? McCain's 2008 running mate Sarah Palin might be one of the few potential contenders who has greater name recognition than Romney. The former Alaska governor rates high among Republican voters, but is very polarizing among independent and Democratic voters, meaning she could win the Republican nomination but have a much tougher time in the general election.
Palin's "One Nation" bus tour, which she insists is not the prelude to a presidential announcement, "coincidentally" was rolling toward New Hampshire as Romney was making his announcement.
And while she wasn't campaigning, Palin used a stop in Romney's hometown of Boston to weigh in on the newly announced candidate, equating the Massachusetts health care plan as a "government mandate" and saying he would have a hard time justifying it with conservatives.
"In my opinion, any mandate coming from government is not a good thing, obviously and I am not the only to say so, but obviously there will be more explanation coming from Gov. Romney for his support of government mandates," Palin said.