President Obama announces support for building an oil pipeline from Oklahoma to Texas, Thursday in Cushing, Okla. Tom Pennington/Getty Images hide caption

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President Obama greets students after speaking at the University of Michigan in Ann Arbor on Jan 27. Young Republicans say they see an opportunity in 2012 to dent Obama's popularity among the youngest voters. Jewel Samad/AFP/Getty Images hide caption

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Former Pennsylvania Sen. Rick Santorum speaks at the Bella Donna Chapel in McKinney, Texas, on Wednesday. Rex C. Curry/Associated Press hide caption

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Men arrive at a campaign rally for Mitt Romney in Elko, Nev., on Friday. Emmanuel Dunand/AFP/Getty Images hide caption

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