WASHINGTON -- Rick Santorum grew wealthy over his four years working as a corporate consultant and media commentator after leaving the Senate in 2006, his newly released federal tax returns show.

He made more than $3.6 million and drove an Audi, details that could be at odds with his effort to attract blue-collar voters in the GOP's upcoming presidential primary in Michigan.

Santorum, 53, has presented himself 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 detail the trajectory of a politician who became a millionaire, at times by capitalizing on his Beltway connections.

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

The returns show that his tax payments rose from $167,000 in 2007 to $310,000 in 2009, then fell to $263,000 in 2010. He paid a combined tax rate of about 28 percent over the four years, putting him in the company of many upper middle-class Americans, but not in the 35 percent bracket of the highest wage earners.

Santorum's wealth doesn't come close to Mitt Romney's multimillion-dollar fortune. But Santorum's 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 2010 tax returns show he made more than $550,000 in media and consulting fees. The previous year, Santorum made more than $820,000 in such fees. In his presidential financial disclosure spanning 18 months between 2010 and 2011, he also listed $1.3 million in income as a consultant, much of it from media appearances and corporate work for health care, energy and social conservative interests.

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