Who Will Control The Senate?

The race for the White House could determine it:  

[P]residential coattails could be key, and we can’t over-stress the importance of the presidential race on the battle for the Senate. This is a hyper-partisan era, and one effect of party polarization is a reduction in ticket-splitting in years like 2012. A Senate candidate in a competitive race will have difficulty swimming against a strong presidential tide in most of these states.