Get ready for the riots.
Several months back I posted here that we'd know Obama is going to lose when whispers of "unrest" begin to pop up. I imagine about two or three weeks before the election is the crucial time. It'll be the only card liberals have left to play and, of course, they'll deal it from the bottom of the deck. Keep your ears open.
On a related note, I did hear a reporter a week or so ago say to Romney that a lot of people would be disappointed if the first black President lost, and how was he (Romney) going to be a President for all the people. That may have been the start.