Rep. Paul Ryan, who has been chosen by Mitt Romney to be his running mate on the GOP ticket, greeting supporters Sunday in his home state of Wisconsin. Ryan will be in Iowa today. Saul Loeb/AFP/Getty Images hide caption

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President Obama meets with Jason and Ali McLaughlin and their son, Cooper, while visiting their home in Cedar Rapids, Iowa. Susan Walsh/AP hide caption

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President Obama tours Conveyor Engineering and Manufacturing in Cedar Rapids, Iowa, on Wednesday. Jewel Samad/AFP/Getty Images hide caption

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Republican presidential candidates at the "Thanksgiving Family Forum" in Des Moines on Nov. 19, 2011. Brad Horn/NPR hide caption

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How much is it worth?

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