A race-by-race analysis of the Senate, in fact, suggests that Republicans might now be close to even-money to win control of the chamber after next year’s elections. Our best guess, after assigning probabilities of the likelihood of a G.O.P. pickup in each state, is that Republicans will end up with somewhere between 50 and 51 Senate seats after 2014, putting them right on the threshold of a majority.
...
In a strong Republican year, the G.O.P. could win all of the tossup and “lean Democratic” seats and pick up one of the “likely Democratic” seats like New Hampshire, which would give them a net gain of nine seats and leave them with a 55-45 majority in the chamber. In a strong Democratic year, the party could lose only West Virginia and South Dakota – and pick up New Jersey and one of Kentucky and Georgia – and hold their current 54-46 edge. It is therefore important to watch macro-level indicators – especially Mr. Obama’s approval ratings, the generic Congressional ballot and major economic measures – in addition to following the recruitment and polling in individual states.
