Nate Silver: Republicans have a 3 in 4 chance of winning control of the Senate

Nate Silver has released his final predictions for tonight's midterm elections, and he estimates Republicans have a 76 percent chance of winning the Senate.

Silver notes, however, that the race may not be "called" for Republicans on Tuesday — "the outcome of the Senate may not be determined until days or weeks from now," thanks to runoffs and other factors. He estimates, though, that Republicans will be in control of the Senate when it convenes in January.

For Democrats to keep control of the Senate, meanwhile, Democratic candidates would need to win two or three key races "where they are underdogs," Silver notes. Attention is on Alaska, Colorado, Iowa, Kansas, Louisiana, New Hampshire, and North Carolina, where neither party has established a 95 percent chance of winning.