The thing I find surprising about literacy tests is that they probably could be brought back without constitutional problems. Sure, the Supreme Court has stopped states from using literacy tests to keep racial minorities from voting. For example, it wasn't OK for southern states to combine impossible to pass literacy tests  with grandfather clauses that said if your grandfather was eligible to vote (i.e. not a slave) then you could wave the impossible test. But literacy tests applied without racial discrimination have always [been upheld]. It was a law, specifically the Voting Rights Act of 1965, that banned literacy tests, not some Supreme Court ruling. And really, that national ban is probably on shakier constitutional grounds than any neutrally applied literacy test.     So yeah, I still don't think it's a good idea because people would immediately abuse their power to write the test questions, but it would only take a change in legislation to bring the tests back.