Voters cast ballots in Dearborn, Mich. Some political analysts say truly independent voters account for just 10 percent to 15 percent of the electorate. Paul Sancya/AP hide caption

itoggle caption Paul Sancya/AP

A neighborhood watch sign stands outside The Retreat at Twin Lakes, the gated community in Sanford, Fla., where Trayvon Martin was shot by George Zimmerman on Feb. 26. Roberto Gonzalez/Getty Images hide caption

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Students at Gardena High School in Gardena, Calif., lined up for a security check before school in January 2011. Nick Ut/AP hide caption

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People wait in line to get into a job fair in Independence, Ohio, in November. Tony Dejak/AP hide caption

itoggle caption Tony Dejak/AP

Fans of GOP presidential candidate Ron Paul show their support outside the Mesa Arts Center before Wednesday night's Republican debate in Mesa, Ariz. Ethan Miller/Getty Images hide caption

itoggle caption Ethan Miller/Getty Images