Here’s the whole text:
Many, if not most, political analysts are talking about the Republican tsunami due on November 2. According to current projections at FiveThirtyEight, Republicans are expected to capture 7 Senate seats, 50 House seats, 6 Governorships. Analysts are calling this the biggest year since 1994. Michael Barone says it may be even bigger than that:
“For months, people have been asking me if this year looks like ’94. My response is that the poll numbers suggest it looks like 1994, when Republicans gained 52 seats in a House of 435 seats. Or perhaps somewhat better for Republicans and worse for Democrats. The Gallup high turnout and low turnout numbers suggest it looks like 1894, when Republicans gained more than 100 seats in a House of approximately 350 seats.”
Maybe the results will be closer to Michael Barone’s high-end prediction than RCP and FiveThirtyEight. To betray my political affiliation, as if you didn’t already know, I hope it is. But currently, the polling suggests it won’t be. FiveThirtyEight’s statistical analysis has the Republicans winning 228.4 House seats. RCP hs the Republicans at 235.5 if we give half the Toss Ups to the Republicans. So based on current projections, the Republicans will win 52.5% or 54.1% of all House seats. Currently, the Democrats have 255 House seats or 58.6% of them. For Republicans to match the Democrats’ current position, Republicans would have to win 77 House seat. (Remember, all House seats are up for grabs each two-year election.)
This certainly puts the “tsunami” into perspective. While this election may be called a tsunami based on the number of seats changing hands, I would not call it an outright tsunami when Republicans are not likely to win as many seats in 2010 as Democrats did in 2008.
This tsunami vs. non-tsunami picture can be seen as either good news or bad news for Republicans (and inversely for Democrats).
From the one perspective, it would be very disappointing that the Republicans can only manage 52.5% (FiveThirtyEight) or 54.1% (RCP) of the House seats in a tsunami year. How can the Republicans “fix” Washington and the country when they cannot win the large majorities that the Democrats have been able to?
From another perspective, this may mean that the polls, RCP, and FiveThirtyEight are way off and that some predictions of even larger Republican gains will come true. The generic Congressional polls currently gives the Republicans a 7.2% advantage. However, if you eliminate the three oldest polls in the average, Republicans have a 9.8% advantage. That would imply a Republican vote total of 54.9%. In 2006, the Democrats won 53.6% of the total vote and captured 53.6% of the House seats in an election that switched party control. So, even with the benefits of incumbency, each party should receive the number of House seats equal to its vote total. Therefore, based on the generic Congressional polls, Republicans should win 54.9% of the House seats, giving them 239 seats, a 61 seat gain.
Let’s look at an alternative scenario. What is Gallup’s most Republican-favorable margin of victory plays out? If Republicans do indeed win by seventeen point, they would win 58.5% of the total vote and about the same number of House seat. That would results in 254 Republican seats, a gain of 76 seats. That would be huge, a tsunami as they are saying, but nowhere near the 100 seats Michael Barone said is possible.
Now what if the low end model plays out; the one where Republicans only win by five points? The Republicans would then capture about 228 seat, a gain of 50 seats.
So here is my official prediction for the House of Representatives:
Republicans gain 61 seats and finish with 239 seat, about 55% of the total. This is more than the 50-seat gain predicted at FiveThirtyEight and the 58-seat gain predicted by RCP, but less than some others are talking about. On the low end, I would expect Republicans to win 50 seats. So my low end projection is equal to FiveThirtyEight’s middle-of-the-road projection. On the high end, I think it unlikely that Republicans win more than 76 seats*, much less than some are saying is possible. (I will update this prediction in the comments section as new polls come in.)
* All that said, this election is probably the most difficult to model in years, possibly ever, and the polls and models they are based on are less accurate than most years. The gap between Gallup’s registered voter and likely voter (lower turnout) models is a huge 12 points. Nobody know which model, if any, is the best and therefore the range of possible results this election is huge. But lacking anything better than the current polls and models, I used those.
I think the only part your analysis may have missed is that statistically speaking, the further you deviate from the 50/50 split, the higher the end result in seats won will deviate from the vote total.
To draw an extreme example, a party that gets 5 percent of the popular vote will not have have won 5% of the congressional seats, it will be lucky to have 1 seat.
A party that gets 25% of the popular vote will not win 25% of the congressional seats, they will be lucky to win 10%.
Think of it as the normal distribution curve, with the vote split being the line on the bottom and the number of seats as the area under the curve.
So while at 53/47 split you might see a seat split close to 53/47, if the split goes to 58/42 or 59-41, you will see a split in seats that is higher than 58/42.