Mitt Romney, the former Republican governor of Massachusetts, announced on Thursday that he will run for the White House next year.
He accused President Barack Obama of mishandling the economy.
Opinion polls suggest Romney is the favourite to win the Republican nomination.
Romney said Obama’s policies had left America “only inches away from ceasing to be a free-market economy.”
The 64-year-old failed to gain his party’s nomination in the primaries four years ago, losing out to John McCain.
Romney once ran Bain Capital, a private equity firm, and put 27 million euros of his own money into financing his unsuccessful presidential bid.