The Star Tribune reports:
Legions of lawyers are ready to enter the fray in case Election Day turns on a legal challenge. One nightmare scenario would be for the results in a battleground state like Florida or Ohio to be too close to call, with thousands of absentee or provisional ballots yet to be counted.
The key, experts say, is whether the difference in votes between the two candidates is within what's known as the "margin of litigation" — that is, the number of outstanding votes must be much greater than the margin separating Obama and Romney when the smoke clears. And, it must be in a state that's decisive.
"You'd have to have a state whose Electoral College votes are absolutely pivotal or there would have to be a massive problem involving voters," said Richard Hasen, law professor at the University of California, Irvine, and founding editor of the Election Law Journal. "There not only have to be problems in an election. They have to be widespread enough or the margin close enough that litigating would actually make a difference."