LANSING, Mich.—It's a day full of campaigning for Mitt Romney in Michigan, his native state, as he looks for a victory in Tuesday's GOP presidential primary against surging Rick Santorum.

Romney focused on President Barack Obama during a breakfast event Saturday in Lansing. Romney is promoting lower taxes and spending cuts while accusing the Democratic incumbent of failing to tackle the nation's economic woes.

But Romney also is challenging Santorum's commitment to conservative principles in light of votes the former Pennsylvania senator says he now regrets.

Romney says the 2012 election is "an election about the soul of America."

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