Nate Silver: "Let me declaim that the utterly fascinating special election in NY-23 has become nearly impossible to forecast. Special elections, with their low turnout, are intrinsically pretty difficult to predict. So are multi-candidate races. And certainly, races where there are substantial late-breaking developments -- such as the Republican candidate dropping out four days before the election and endorsing her Democratic rival -- present especial difficulties for forecasters. Here, you have all three of those circumstances, producing a perfect storm of uncertainty."