From Ed Felten…

Long lines to vote: Polling places will be strained by the number of voters. In some places the wait will be long – especially where voting requires the use of machines. Many voters will be willing and able to wait, but some will have to leave without casting votes. Polls will be kept open late, and results will be reported later than expected, because of long lines.

Registration problems: Quite a few voters will arrive at the polling place to find that they are not on the voter rolls, because of official error, or problems with voter registration databases, or simply because the voter went to the wrong polling place. New voters will be especially likely to have such problems. Voters who think they should be on the rolls in a polling place can file provisional ballots there. Afterward, officials must judge whether each provisional voter was in fact eligible, a time-consuming process which, given the relative flood of provisional ballots, will strain official resources.

Voting machine problems: Electronic voting machines will fail somewhere. This is virtually inevitable, given the sheer number of machines and polling places, the variety of voting machines, and the often poor reliability and security engineering of the machines. If we’re lucky, the problems can be addressed using a paper trail or other records. If not, we’ll have a mess on our hands.

How serious the mess might be depends on how close the election is. If the margin of victory is large, as some polls suggest it may be, then it will be easy to write off problems as “minor” and move on to the next stage in our collective political life. If the election is close, we could see a big fight. The worse case is an ultra-close election like in 2000, with long lines, provisional ballots, or voting machine failures putting the outcome in doubt.

Let’s hope the opinion polls are right. The omens are not good on the voting machine front.