Here NPR lays out the math for readers on the 2014 senatorial elections. It looks like the GOP will make some progress in taking back the upper chamber.
There are 20 Democratic and 15 Republican seats in play, and, at this point, the seats in danger of flipping are almost all Democratic.
A growing consensus is that the four most winnable-for-Republicans races include, for the moment, South Dakota, Montana, and West Virginia, where Democratic senators are retiring; and Arkansas, where Democratic Sen. Mark Pryor is the party’s most vulnerable.
No Republican-held seat appears to be flippable yet, with the exception of New Jersey, which will likely revert to Democratic control in an October 2013 special election. A Republican appointee has briefly held the New Jersey seat left vacant by the death in June of Democratic Sen. Frank Lautenberg.