What about House races? It has generally been assumed, and for good reason, that Republicans have little possibility of substantial gains because they did so well in 2010, when they won 242 seats, more than in any election since 1946, and in 2012, when they won almost as many, 234. And it has been noted that the retirement of incumbent Republicans in Iowa’s third district, New Jersey’s third, Pennsylvania’s sixth and Virginia’s tenth give Democrats a good chance of winning some seats, on top of California’s 31st (where California’s all-party primary law left the 2012 race as a contest between two Republicans in a 57-percent Obama district). Against that must be weighed Republicans’ near certain chance of picking up North Carolina’s seventh and Utah’s fourth, where Democratic incumbents who won by one percent in 2012 retired, in districts where Mitt Romney won 59 and 68 percent of the vote.

Now, however, the National Republican Congressional Committee has released four polls, also conducted by the Republican Harper firm, which suggest that Obama’s weakening job approval and the negative reaction to Obamacare may be expanding the field to the Republicans’ advantage…

These results provide support for the proposition that Republicans could win a fair number of House seats not previously thought to be in play — though it should be kept in mind that these are polls conducted by a Republican firm for a Republican party client, and that the NRCC may be sitting on results in other districts that look less favorable for their side. No political operatives have an obligation to reveal unfavorable poll results, and very few do. It should also be said that polling Steve Israel’s district shows a certain puckishness and perhaps, in some Democrats’ minds, childish prankery; he won his last race 58-42.