On PBS's NOW, a story broken by BBC correspondent Greg Palast:
It seems that in 2004 the Republican Party had a plan to challenge the voter registrations of thousands of newly registered voters. They sent out junk mail letters to newly registered voters, and if these letters were marked "Return to Sender" they intended to use this as evidence to challenge the legality of the votes of new voter registrants (who did not vote Republican). They were targeting African American voters with these letters -- most blacks vote Democratic. Also targeted were overseas servicemen. This is called "Voter Caging."
Insiders say there was a plan to use the power of the Department of Justice to challenge newly registered voters. It turns out that at least one of 9 attorneys fired by the Bush administration -- David Iglesias -- had been asked to investigate liberal voter-registration advocacy groups such as Acorn. Effectively, Iglesias claims he was fired for his refusal to prosecute bogus allegations of voter fraud (for more background to this story, see this Jotman post). This fired attorney is convinced the White House was behind this illegal scheme to suppress African Americans from voting.