Republicans now have approximately a one-in-four chance of winning enough Senate seats in the Nov. 2 elections to claim an outright majority of the chamber, FiveThirtyEight’s latest forecasting model shows.
That the composition of the Senate is in doubt is not a new development; the model had assigned Republicans better than a one-in-five chance of claiming the chamber upon its debut at The New York Times two weeks ago. Nevertheless, nearly every day now seems to bring another sour piece of polling news for the Democrats.
Today, for instance, a poll for The Washington Post showed Republicans with a 13-point lead among likely voters on the generic Congressional ballot, which would imply a potentially catastrophic outcome for Democrats. Although the polling trend is not always uniform or predictable — Gallup’s generic ballot poll, which had given Republicans a 10-point advantage last week, now shows the two parties running evenly — the Democrats’ hopes for a spontaneous political recovery this summer now appear to be dashed.
Although the generic ballot is used to help calibrate FiveThirtyEight’s Senate model, most of its inputs are polls of individual Senate races. There, the news is somewhat more mixed. Although polls have come out in the last two weeks showing the Republican nominee in Kentucky, Rand Paul, with an increasingly large lead, and Pat Toomey, the G.O.P. nominee in Pennsylvania, with an expanding advantage over his Democratic opponent, Representative Joe Sestak, a recent poll in Colorado showed the Democratic incumbent, Michael Bennet, with a slight lead. And the model now regards Harry Reid as a slight favorite to retain his seat in Nevada, which was not the case two weeks ago.
Also, although it has become easier — perhaps more than ever — to envision a Republican path toward taking over the Senate, they still remain underdogs and have, in essence, two significant hurdles to clear. The first hurdle is purely statistical: polls are relatively fuzzy instruments prior to Labor Day, before many voters have engaged with the campaigns. And in the weeks immediately leading up to Labor Day — when many Americans are on vacation — they can be especially erratic. If, in two or three weeks, the polls continue to show clear signs of Republican momentum, their prospects for a Senate takeover will be more robust.
The other hurdle is more tangible: there are a series of competitive Republican primaries, in which candidates supported by the Tea Party are pitted against more moderate alternatives.