This makes sense: Midterm elections tilt older and whiter than presidential elections — which is to say, they tilt toward Republican constituencies. So Democrats will start off on a more level playing field. Moreover, choice elections tend to be better for incumbents than referendums. Obama’s name on the ballot — not to mention the presence of a single Republican opposing him — will make it much easier to fire Democrats up. Given those two factors, it’s easy enough to imagine the circumstances in which the House goes Democratic. It might not be likely, but it’s not unimaginable. All House Democrats need to do, after all, is win 51 percent of their races.

The Senate is going to be a more uphill battle. Democrats can’t win back any of the seats they lost in 2010 — those seats won’t be up until 2016. And because the seats up in 2012 were won in the Democratic wave of 2006, Democrats will be defending 23 seats to the Republican’s 10. That means for Democrats to hold the Senate, they’ll need to win almost 60 percent of those races — which is obviously a tougher charge.

All of which is to say, if Democrats have a good year in 2012, it’s likelier that 2013 sees President Obama working with Speaker Nancy Pelosi than President Obama linking arms with Majority Leader Harry Reid. It helps explain, I think, why Pelosi was so intent on remaining leader of the House Democrats after last year’s rout, and also why Reid was so unwilling to make any significant changes to the Senate’s rules.