In the Senate elections, the campaign math is not favoring the Democrats. Simply put, Democrats have many more vulnerable seats up for grabs next November than Republicans do. Democrats control 23 of the 33 seats up for election next year—and at least six senators who caucus with the Democrats are going to retire, while two more Democratic incumbents have yet to confirm whether they will run for re-election. The number of Republican senators who are not up for re-election this cycle, meanwhile, is just two.
In the House elections, the 2010 Census looms over the 2012 elections—in a way that again favors the Republicans. In the first election after every census the government reapportions the seats between the states to reflect population shifts. In general, seats were lost in the Northeast and Midwest, where Democrats have traditionally performed well; and the Southeast and Southwest—traditional strongholds for the GOP–gained seats. Republicans control most of the state legislatures in the 10 states picking up additional House seats– including 4 seats in the heavily Republican state of Texas–the new congressional districts will likely be drawn up with boundaries favoring the Republicans. That is the simplest kind of political math.