One prominent scenario that is the focus of a "hanging chad" analysis is in Ohio.

Nightmare scenarios haunt election season
http://www.journalgazette.net/article/20121019/NEWS03/310199985/1006/news

"269-269 Electoral College tie is unlikely but far from impossible. It could result, for instance, if Romney wins all the competitive states except Ohio, Wisconsin and New Hampshire. There has never been an Electoral College tie.

But that isn’t the only nightmare scenario that could raise doubts about the election’s fairness.

Campaign activists in many states are bracing for possible confusion, delays and even confrontations in polling places Nov. 6. They are particularly watching Democratic-leaning precincts where Republicans may challenge some people’s eligibility to vote.

In recent years, Republican officials in several states have pushed for tighter voter restrictions, including requirements for photo identifications and reductions in the amount of time allowed for early voting. Republicans say they are trying to prevent voter fraud.

Democrats, however, note the absence of proven cases of serious election fraud. They say the GOP actions are meant to suppress voting by Democratic-leaning groups such as blacks, Hispanics, low-income people and college students."



Presidential race could hinge on Ohio's delayed provisional ballots

http://www.courier-journal.com/article/20121025/NEWS0106/310250024/Presidential-race-could-hinge-Ohio-s-delayed-provisional-ballots

"Under Secretary of State Jon Husted’s initiative to send absentee ballot applications to nearly 7 million registered voters across Ohio, more than 800,000 people so far have asked for but not yet completed an absentee ballot for the Nov. 6 election.
Anyone who does not return an absentee ballot, deciding instead to vote at the polls, will be required to cast a provisional ballot. That’s so officials may verify that they did not vote absentee and also show up at the polls.
By state law, provisional ballots may not be counted until at least Nov. 17. That means that if Ohio’s electoral votes would be decisive in the race between President Barack Obama and former Massachusetts Gov. Mitt Romney, the state could keep the nation in suspense for several weeks after the election."

"That would be called my nightmare scenario,” said Amy Searcy, director of the Hamilton County Board of Elections.
But it is also, election experts warn, a distinctly possible scenario if the vote in Ohio – and nationwide – is close.
“We could easily see a situation in which the nation has to wait for Ohio because of provisionals,” said Ed Foley, an Ohio State University law professor and nationally respected expert on election law. “We ought to start thinking about those what-if scenarios now rather than the Wednesday morning after the election.”