With Texas lawmakers likely to debate a new law requiring proof of citizenship to register to vote, a top voting-rights group warns the plan could block "millions" of eligible people from casting ballots. A recent study by the nonpartisan organization VoteRiders shows that 1.3 million Texans who are U.S. citizens of voting age — or about 7% — would have difficulty showing documentation that proves their U.S. citizenship. "Requiring documentary proof of citizenship in Texas risks disenfranchising millions of voters," said Selene Gomez, national outreach director for VoteRiders.