Polling shows that voters have much more negative feelings toward congressional Republicans than congressional Democrats. Postelection polls have shown Democrats ahead of Republicans on the generic ballot — which party’s candidate for the House would you vote for?

All but one of those polls was conducted by Scott Rasmussen, most of whose polls before the 2012 election showed the parties about even in the generic ballot. Rasmussen’s most recent survey shows the gap closing, but that’s just one poll and could be statistical noise.

So there’s a case to be made that the Democrats can win back the majority. But there’s also a case to be made that they can’t, or at least that it will be very hard.

The crux of that case is that the playing field favors the Republicans. Only 16 of the 234 House Republicans represent districts carried by Barack Obama.