Incumbency was the Democrats best weapon in all of these races, but that edge almost immediately began to slip. Five-term incumbent Sen. Jay Rockefeller, D-W.V., announced in January that he would not seek reelection, giving Republicans a smoother pick-up opportunity (Romney won the sate by 26 points). Then this week, three-term incumbent Sen. Tim Johnson, D-S.D., announced his retirement, thus making another path easier for Republicans (Romney won the state by 18 points).

Many of the Democratic incumbents in the other five red states (Sens. Mark Begich, Alaska, Mark Pryor, Ark., Mary Landrieu, La., Max Baucus, Mont., and Kay Hagan, N.C.) also were put in a tough spot when billionaire New York City Mayor Michael Bloomberg began running $12 million in television ads pressuring senators to support strict new gun control laws at the federal level. Pryor, Landrieu, and Hagan were all specifically targeted. These Democrats will need both pro- and anti-gun Democrats to turn out for them in 2014 if they have any shot of holding onto their seats. Bloomberg just made that harder.