I actually think Paul Krugman puts the wrong spin on Andrew Gelman's graph showing that House Democrats broadly outperformed Barack Obama:
The downticket performance of House Democrats isn't what strikes a fairly mortal blow to the "center-right" theory of American political preferences. Rather, it's the fact that for the first time since 1960, the presidential level Democrat is almost matching the performance of downticket Democrats. Downticket elections are different than national elections. A well-liked local leader who happens to a Democrat can win in a conservative district. This is why you see, for instance, Democratic governors in Wyoming, even as Wyoming is utterly out of reach for a Democratic presidential candidate. National elections are more about comfort with the national parties. A strong Democratic Party has to not only be able to win on the more local level, but win on the presidential level, where affiliation is more important. In the 1990s, the party was winning on the presidential level, but being massacred in the downticket races. It couldn't appeal locally. In the 80s, it was just the opposite. It couldn't appeal nationally. And without the mixture of executive power and legislative power, it couldn't do very much. But for the first time in decades, we're seeing a Democratic Party that's able to win locally and nationally. Which suggests we're finally seeing an electorate exhibiting an actual preference for the Democratic Party as an institution. This ism of course how you actually get power.
The downticket performance of House Democrats isn't what strikes a fairly mortal blow to the "center-right" theory of American political preferences. Rather, it's the fact that for the first time since 1960, the presidential level Democrat is almost matching the performance of downticket Democrats. Downticket elections are different than national elections. A well-liked local leader who happens to a Democrat can win in a conservative district. This is why you see, for instance, Democratic governors in Wyoming, even as Wyoming is utterly out of reach for a Democratic presidential candidate. National elections are more about comfort with the national parties. A strong Democratic Party has to not only be able to win on the more local level, but win on the presidential level, where affiliation is more important. In the 1990s, the party was winning on the presidential level, but being massacred in the downticket races. It couldn't appeal locally. In the 80s, it was just the opposite. It couldn't appeal nationally. And without the mixture of executive power and legislative power, it couldn't do very much. But for the first time in decades, we're seeing a Democratic Party that's able to win locally and nationally. Which suggests we're finally seeing an electorate exhibiting an actual preference for the Democratic Party as an institution. This ism of course how you actually get power. 
