The Democrats will "win" today, because of cellphones:

A lot of American adults (now about one-quarter of them) have ditched landlines and rely exclusively on mobile phones, and a lot of pollsters don’t call mobile phones. Cellphone-only voters tend to be younger, more urban, and less white — all Democratic demographics — and a study by Pew Research suggests that the failure to include them might bias the polls by about 4 points against Democrats, even after demographic weighting is applied.