As the nation gears up for the 2012 presidential election, Republican officials have launched an unprecedented, centrally coordinated campaign to suppress the elements of the Democratic vote that elected Barack Obama in 2008. Just as Dixiecrats once used poll taxes and literacy tests to bar black Southerners from voting, a new crop of GOP governors and state legislators has passed a series of seemingly disconnected measures that could prevent millions of students, minorities, immigrants, ex-convicts and the elderly from casting ballots.