You don't need to present papers when you register to vote but the registrar will check the name and info before you are listed as elgible to vote. Once you are on the rolls they only seem to seek minimal ID (such as your utility bill or the voter pamphlet mailed to your house) but the registrar is supposed to verify that you are a citizen before you are on the list. I suppose that if somebody got a copy of your utility bill and went to your polling place they could vote illegally but the chances are extremelly small. Illegal aliens are not voting.
There are other games that are played. In the last election cycle there was a group of people who were supposed to be trying to sign up Republicans before the election - and they were tossing out anybody who signed up with them as Democrats. When the Dems showed up at the polls, the obviously could not find their names listed.
http://www.8newsnow.com/Global/story.asp?S=2421595