WASHINGTON (AP) — Republican presidential candidate Rick Santorum released four years of federal income tax returns on Wednesday night, showing a sharp rise in his personal wealth spurred by his growing work as Washington-based corporate consultant and media commentator.

Santorum, 53, has sold himself in the Republican primaries as both a social conservative and a Washington outsider, stressing his family's coal-mining background and his appeal to religious and working-class voters. His personal finances tell a different story, detailing the trajectory of a politician who grew more prosperous in the Senate and became a millionaire afterward, at times capitalizing on his Beltway connections.

The former Pennsylvania senator's tax returns show that his annual income surged from nearly $660,000 in 2007 to $1.1 million in 2009 before slipping to $923,000 in 2010.

Santorum's wealth doesn't come close to the multimillion-dollar fortune amassed by Mitt Romney's high-finance prowess or Newt Gingrich's smaller but still-lucrative blend of foundation and consulting work. But his newfound affluence reflects his close ties to Washington's business and lobbying circles during his 12 years in the Senate and his smooth transition into their world after he left office.

His federal income taxes rose from 2007, when he paid $167,000, to $310,000 in 2009, then dropped to $263,000 in 2010. Santorum paid a combined tax rate of 28 percent over the four years, putting him in a high tax bracket but not in the top 35 percent. Gingrich paid an estimated 31 percent, according to his federal returns, while Romney paid 14 percent because many of his earnings came from investments taxed at a lower capital gains rate. Both Romney and Gingrich recently disclosed income tax returns.

Santorum's 2010 tax returns show he made more than $550,000 in media and consulting fees — paid to him through a corporation he set up, Excelsior LLC. The previous year, Santorum made more than $820,000 in fees, also paid through the same firm.

Last year, Santorum disclosed investment and real estate assets totaling as much as $2.5 million. In his presidential financial disclosure spanning 18 months between 2010 and 2011, Santorum also listed $1.3 million in income as a consultant — much of it coming from media appearances and corporate work on behalf of health care, energy and social conservative interests.

Rising to GOP leadership in the Senate as Republican Conference chairman, Santorum pushed to expand the influence of Republican-leaning business interests. As conference chairman, he headed GOP Senate communications efforts and met regularly with GOP-leaning business and lobbying figures. He raised more than $550,000 from lobbyists during his unsuccessful 2006 Senate re-election campaign.

After his Senate defeat, Santorum did not register as a lobbyist, but he aided corporate and other interests as a consultant. He was paid $142,500 by Consol Energy, a Pennsylvania-based energy firm with numerous Appalachian coal mines. The firm has lobbied against Obama administration efforts to tighten limits on greenhouse gas emissions.

Santorum also was paid $65,000 by the American Continental Group, a D.C. lobbying firm with an assortment of corporate clients, and $125,000 by the Clapham Group, a Virginia firm that aids religious rights organizations. He benefited from media work, earning $230,000 for appearances on Fox News and more than $80,000 for stints as a radio commentator.

Santorum was also paid nearly $400,000 in compensation and stock options as a board director at Universal Health Services, a hospital management firm, after he left the Senate in 2006. He also owns up to $250,000 in Universal stock. As a senator, Santorum had sponsored several unsuccessful bills that would have secured more Medicaid funding for hospitals run by Universal and other medical firms in Puerto Rico.

Santorum also owns five rental properties in State College, Pa., worth $500,000 and $1.25 million, but also with as much as $750,000 in mortgage debt, according to his presidential disclosure. His taxes show that he took mortgage and depreciation deductions on those properties, and also that he sold more than $23,000 worth of stocks in 2010.

Santorum and his wife, Karen, took standard deductions each year for their seven children, the returns show. In 2007, the Santorums took a $4,000 charity deduction for giving away "clothing, footwear, accessories and household items." That year, the family moved into a larger home in the Virginia suburbs of Washington.

Santorum and his family now live in a four-bedroom northern Virginia house on five acres assessed at $1.4 million in 2010.

The tax returns were first made available Wednesday night by Politico.