Larry Sabato handicaps the 2014 midterm elections:
At this early stage, the combination of these three factors [ed. i.e. the president’s declining approval rating, the economy, and the electoral playing field] suggests a good election year for the GOP. The president is a Democrat and his approval is weak. The economy may be improving, based on GDP growth (4.1 percent in the third quarter), but voters still don’t believe their personal economy, at least, has picked up much. Instead, the major national issue of the moment is Obamacare, which at this point is a loser for Democrats. The structure of the election in the House and Senate also bends in the GOP direction.
I continue to think that the greatest likelihood is that the Republicans will hold the House and gain no more than five seats in the Senate, narrowly failing to take control of that house.