Voter registrations could be checked against the Social Security database. Not only would non-citizens be spotted, duplicate registration would end immediately.
That's actually a really awful idea. Firstly: not everyone has a social security number. For example, some Amish refuse to get one. They are still citizens of this country, and should be allowed to vote. The numbers are required to file income tax returns. Whatever provisions the IRS makes for the Amish would apply to checking voter registration.
Presumably, they would have to a driver's license with your name on it. If someone actually succeeded to that point, you wouldn't lose your right to vote, but, the other person would be in serious legal jeopardy.
One person registering and voting in the same election more than once is "a problem." There is simply no tolerable level of voter fraud.
