Republican presidential hopeful Mitt Romney, who made part of his fortune as co-founder of a private equity firm, and his wife have personal financial assets worth as much as $264 million, according to disclosure documents filed Friday.

The records suggest that Romney may have seen a small, but limited, drop in wealth during one of the nation’s worst economic downturns, with a maximum asset value about 8 percent lower than what he reported during his first White House bid in 2007.

The numbers underscore an issue that poses both a benefit and a challenge for the former Massachusetts governor, who points to his business experience as evidence of his ability to lead the country.

But Romney, who grew up in a wealthy family before expanding his fortunes at the Bain Capital equity firm, also has struggled to portray himself as a candidate in touch with the lives of regular voters.

At an Iowa appearance this week, Romney sparred with hecklers urging him to raise corporate taxes by responding: “Corporations are people, my friend.” GOP challenger Tim Pawlenty also made light of Romney’s wealth during a Thursday night debate in a quip about mowing his lawn.

Romney is far richer than most, if not all, of his presidential rivals. President Obama and first lady Michelle Obama reported assets between $2.8 million and $11.8 million in 2010. The only other candidate who might exceed Romney in personal wealth, former Utah governor Jon Huntsman Jr., has yet to file a disclosure.

In addition to his sprawling investments, Romney was paid more than $374,000 for nine speeches in 2010 and 2011, including a speech at Clark Consulting in Half Moon Bay, Calif., for $66,000 and two appearances worth $68,000 each for Goldentree Asset Management and the International Franchise Association.

His most recent reported speech, for Barclay’s Bank in Washington, made him $42,500 in February, as he was preparing for the start of his presidential campaign, the records show.

Romney also owns horses worth up to $500,000 through a limited-liability company; one of them won a prize of less than $201, the report shows.

The financial disclosures — which are expressed in broad ranges rather than precise numbers — suggest that Romney could be worth as little as $85 million or as much as $264 million. His campaign said that “a more accurate range” is between $190 million to $250 million.

Campaign officials said the holdings of Romney and his wife, Ann, are managed in a blind trust administered by an attorney at Ropes & Gray in Boston, a firm long tied to the Republican candidate and his inner circle. “They do not control the investment of these assets,” said campaign spokeswoman Gail Gitcho.

Romney’s investments span a broad spectrum of the global economy, including energy, finance, health care, industrial firms and telecommunications and high technology, the records show.

His assets are held in more than 160 funds controlled by a variety of major investment firms, including BNP Paribas, Goldman Sachs, Rabobank Nederland and Bain Capital. Romney also reported up to $500,000 in Ford Motor Co. stock and up to $250,000 in Marriott International.

Romney earned $113,880.73 for serving as a Marriott director until he resigned in January, the records show. The Marriott family has longtime ties to Romney and brothers J.W. Marriott Jr. and Richard Marriott of Bethesda have each given $500,000 to Restore Our Future, a pro-Romney super PAC that plans to run advertising supporting his candidacy.