Despite media certitude, we do not know who will win the Senate. In The New Yorker, I explain.
From 2004 to 2012, only thirteen Senate races have had margins of less than three percentage points in the week before the election. Of these, four were won by the trailing candidate. One more, the Florida 2004 race, was tied in the polls, and was eventually won by the Republican, Mel Martinez, by 2 percentage points. Scoring that one as half correct, the overall rate of wins by a front-runner is 65%, a bit better than chance.
In light of that, the probability that all six close Senate races (AK, CO, IA, KS, NH, and NC) will be won by the candidate in the lead is only 7%. A wrong call is almost inevitable. We should not be surprised to see one to three races to be won by the candidate who trails this morning. Because of this, the final outcome becomes a game of guess-the-beans-in-the-jar.