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 luxury sedan – 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 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.