The voter is allowed to register at the polls in Wisconsin with little to no identification. Then a follow up letter is sent after the election. There were at least 5,000 new Milwaukee voter registrations returned by the Post Office after the election as "no such person". This does not count the fraud that was perpetrated in Madison or other Dem strongholds. The Milwaukee polls were held open several hours late too. Bush lost Wisconsin by 6,000 votes.
A college student could vote absentee in his own home town and again in person at his college address(es). No one would be the wiser because these are not cross checked. All you need is a piece of mail with your name on it.