Mitt Romney has formally declared his candidacy to challenge President Barack Obama in next year's US election, but the presumed front-runner for the Republican nomination will likely face some big-name competition for his party's backing.
The former Massachusetts governor told supporters gathered on a sunny farm in Stratham, New Hampshire that he would seek the Republican nomination to try to oust the Democratic president in November 2012.
"I'm Mitt Romney and I believe in America. And I'm running for president of the United States," Mr Romney said in announcing his candidacy. He chose to do so in New Hampshire because it has the first-in-the-nation primary vote.
Others could get in his way, because the field of Republicans with presidential ambitions is crowded - and more divided - than usual, with the mainstream being challenged by ultraconservative tea party factions and others with extreme populist views.
Republican political stars Sarah Palin, the former Alaska governor and 2008 vice presidential candidate, and former New York City mayor Rudy Giuliani are both darlings of the conservative wing of the party and both caused a stir of their own with visits to the region.
And rumblings about Texas Governor Rick Perry, New Jersey Governor Chris Christie and Representative Michele Bachmann of Minnesota joining the race could further challenge Mr Romney.
The former governor and business executive aggressively challenged the president while trying to pitch himself to the coalition that makes up the modern Republican Party: fiscal conservatives, social conservatives, evangelicals and libertarians.
Mr Romney, who lost the Republican nomination to John McCain in 2008, hopes it is now his turn, but he will have to convince fellow Republicans. Repeated polls show party members unimpressed with or indifferent to the declared candidates.
Mr Romney's strengths are substantial: He is well known, and he is an experienced campaigner. He has a personal fortune and an existing network of donors. But he must confront his own record of changing positions on social issues including abortion and gay rights, shifts that have left conservatives questioning his sincerity and has also struggled to allay some scepticism of his Mormon faith.
On top of that, Mr Romney championed a health care law enacted in Massachusetts that is similar to Mr Obama's national health overhaul, which conservatives despise.