A "poll test" would be a direct violation of the Voting Rights act of 1965. As a response to the 15th amendment (which said that people could not be denied voting rights on the basis of race), White lawmakers tried all sorts of things to deny Blacks their right to vote. Literacy tests, requirements of property ownership, poll taxes, etc. The Voting Rights Act of 1965 ensured that the right to vote is protected for
all Americans.
It is the right of every American to vote no matter how un-informed or un-scrupulous their vote will be.
Source:
http://en.wikipedia.org/wiki/Voting_Rights_Act_of_1965