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November 1, 2010, *9:35 PM*House Forecast: G.O.P. Plus 54-55 Seats;
Significantly Larger or Smaller Gains PossibleBy NATE
SILVER<http://fivethirtyeight.blogs.nytimes.com/author/nate-silver/>

Republicans are well-positioned to win control of the House of
Representatives in tomorrow’s elections, and quite possibly to achieve the
largest gain made by either party in a Congressional election since World
War II.

Our forecasting model, which is based on a consensus of indicators including
generic ballot polling, polling of local districts, expert forecasts, and
fund-raising data, now predicts an average Republican gain of 54 seats (up
one from 53 seats in last night’s forecast), and a median Republican gain of
55 seats. These figures would exceed the 52 seats that Republicans won from
Democrats in the 1994 midterms.

Moreover, given the exceptionally large number of seats in play, the
Republicans’ gains could be significantly higher; they have better than a
one-in-three chance of winning at least 60 seats, a one-in-six chance of
winning at least 70 seats, and have some realistic chance of a gain
exceeding 80 seats, according to the model.

However, the same factors that could provide Republicans with
extraordinarily large gains if their turnout is strong tomorrow could also
cut against them if Democrats turn out in greater numbers than expected, or
if the polling has underestimated the Democrats’
standing<http://fivethirtyeight.blogs.nytimes.com/2010/11/01/5-reasons-democrats-could-beat-the-polls-and-hold-the-house/>
.

Of the projected Republican gains, many are tenuous. If we allocate all 435
seats to the leader projected by our model — no matter how slim the margin —
Republicans would net a gain of 59 seats. In 15 of these 59 seats, however,
the Republican is projected to win by fewer than 2 points. It is likely that
Republicans will lose at least some of these — which is why the model
forecasts an *average* gain of 54-55 seats, rather than 59, when looking at
the seats on a probabilistic basis. If they lost all of them, however, their
gains would be merely 44 seats, which would put the Democrats within
striking distance of retaining the House. And if Democrats beat their
projected margins by about 3 points across the board, they would be about
even-money to keep control of the House.

Such broad-based errors have occurred before in midterm elections. In 1998,
essentially all key indicators predicted significant Republican gains, but
they actually lost 5 seats to the Democrats. In 1994, on the other hand,
many indicators pointed toward a total Republican gain of 20-30 seats, when
they in fact netted 52 from Democrats.

Our model thinks there is a 16 percent chance of a polling and forecasting
error large enough to allow Democrats to keep control of the House; this
figure is unchanged from earlier this week.

Still, absent such a mistake, Republicans will have much to celebrate. They
are favorites to pick up seats in essentially all regions of the country,
with the possible exception of the Pacific Coast. Longtime Democrat
incumbents like John M. Spratt Jr. of South Carolina and Earl Pomeroy of
North Dakota are likely to lose their seats, and others like Raúl M.
Grijalva and James L. Oberstar now have a 25-30 percent chance of doing so,
according to the model. Some other Democratic incumbents, like Barney Frank
of Massachusetts and Dennis J. Kucinich of Ohio, appear to be considerably
safer, but could fall in a wave that exceeded 70 seats.

We do not perceive any particularly dramatic nationwide movement toward one
or another party in the closing days of the election. There is certainly no
evidence in the polling that Democrats have closed their deficit with
Republicans, but claims that Republicans have expanded their margin are also
tenuous, as generic ballot trends have been roughly
flat<http://fivethirtyeight.blogs.nytimes.com/2010/11/01/agreeing-to-disagree-size-of-republican-wave-hard-to-predict/>
since
Labor Day.

However, it has become abundantly clear that few if any Democrats will be
spared a serious challenge from Republicans, and recent polling has
suggested that some who had seemed to be relatively safe — particularly in
states like New Mexico, Iowa, Maine and Rhode Island, where gubernatorial
races have broken against Democrats — may in fact be quite vulnerable. It is
possible and perhaps somewhat likely that a few Democrats in districts that
have received little polling and little attention will fall. As a slight
counterpoint to this, districts containing Republican incumbents, some of
which might ordinarily be vulnerable, have also received little attention
from pollsters and Democrats could win a few of these, even if they are
having a fairly poor night over all.

This will more likely that not be the final FiveThirtyEight House forecast
of the 2010 cycle, but we would be anticipating re-running the numbers if
significant new polling data becomes available overnight.
--
Eric D. Schwerin
Rosemont Seneca Partners
(202) 333-1880
eschwerin@rosemontseneca.co