Nate Silver updated his Senate forecast and concludes that Democrat Bill Nelson has a 65% chance favorite to win re-election. Conversely, the GOP has a 35% chance of winning, regardless of whether whom is the nominee.
Nationally, “the most likely outcome” is Republicans winning 50 seats, Democrats 49, and Angus King (I) the seat in Maine. Under those circumstances, the Democrats would retain control of the Senate if King caucused with them and President Obama won re-election, making Vice President Biden the tiebreaking vote. Otherwise, Republicans would control the chamber.
However, the range in the forecast is from Democrats winning 55 seats to Republicans winning 56 seats.