In other words, the four special elections, taken as a whole, suggest that Democrats may still be locked in a 2010-type political environment. Democrats might not lose many more seats in the House if that were the case, since most of their vulnerable targets have already been picked off, but it would limit their potential for any gains. And it could produce dire results for the Democrats in the U.S. Senate, where they have twice as many seats up for re-election.

It’s certainly possible to read too much into special elections to the House. Over the long run, they have had a statistically significant correlation to the outcome of the next general election. But the relationship is weak and frequently runs in the wrong direction, as it did in 2010.

Moreover, special elections aren’t a good barometer of the degree of anti-incumbent sentiment, since by definition they don’t feature incumbents on the ballot…

Nevertheless, these are waves that portend trouble.