Nate Silver updates his Senate projections:
Currently, we project the most likely outcome to be Republicans winning 50 seats, Democrats 49, and Mr. King the seat in Maine. Under those circumstances, the Democrats would retain control of the Senate if Mr. King caucused with them and President Obama won re-election, making Vice President Joseph R. Biden Jr. the tiebreaking vote. Otherwise, Republicans would control the chamber.
However, it should be remembered that this is just one potential outcome out of a fairly wide range of possibilities.
The Dish 