Former Wisconsin Governor Tommy Thompson officially joins the race for the White House.
In Madison last month, Thompson headlined a fundraiser for his presidential exploratory committee, but hadn't officially said he was going to run for president until Sunday.
Thompson has focused his strategy on Iowa, where the nation's first caucuses will be held. He's visited the state every week since early December.
The nation’s first straw poll will be conducted there in August. Thompson says he intends to win it. He also says he has to win the Iowa caucus in January to have any chance of gaining the nomination.