The dance card is being rewritten for the 2012 election with two key Democratic Senators bowing out....Connecticut's Joe Lieberman was elected as an Indy in 2006, but caucuses with the Dems...He is not seeking reelection.
Ditto for North Dakota's Kent Conrad, who is getting out of Dodge in 2012 as well. That seat could be a GOP pickup.
The way the seats line up in 2012, Republicans have a good chance at seizing the Senate by virtue of the high number of seats the Democrats are defending in that cycle.
Since I see President Obama likely to be reelected (not my choice, but just the way I see it), that will leave him a second termer facing both houses of Congress in the hands of the other party.