My prediction: Dems will gain
The huge loses people see in their portfolio statements will be the difference. Many rank and file repubs will stay home - demotivated by the rotten economy and Bush's reckless pork barrel spending. Also, I don't think there will be a huge "let's go to war with Iraq" turnout, although the anti-war groups can be expected to vote heavily.
And contrary to popular opinion around here, recounts didn't begin in 2000. Historically, any election that is within 1% has been subject to manual recounts. I hope that is the case this election regardless of who it benefits.