It’s Where You Start That Matters

538 has been trying to correlate the generic ballot with how many seats a party will pick up. Where do the Republicans have to be to pick up the 39 needed seats? I’d read that 2004 was a good Republican year in House votes. That was perplexing. The GOP actually lost 3 seats that year. How can that be a good year? I decided to plot Democratic gains and losses with their share of the House vote.



In 1976 the Democrats got 56.9% of the House vote and gained 1 seat. In 2004 they got 48.9% of the vote and only lost 3 seats. While there is some correlation between percentage of the vote and gains/losses, the chart makes more sense if we look at how many seats the Democrats ended up with after the election.


Now that’s more like it. Since every seat is up every election, the amount they previously had is irrelevant.

There aren’t enough data points to say definitively, but every time the Democrats got 50.9% of the vote or more, they got at least 233 seats. Whenever they got 50.2% or less, they never got above 212. We can extrapolate and predict that Democrats need somewhere between 50.4% and 50.6% of the vote to likely get a majority.

In 2004 the Democrats got 48.6% of the votes and 202 seats. In 2006 they got 54.1% and 233 seats. They needed to increase that share to 55.6% in order to get to 257 seats. Thus, even if Democrats beat Republicans overall by 7 or 8% they’ll likely still lose seats.

What’s interesting is that no matter how bad the Democrats did, they never dropped below 202 seats. Even is 1994 when they were beaten 53.5% to 46.5%. I’m not sure what to make of that. Republicans had over 285 different districts since 1994. So it’s not like all 202 are safe. In fact, in the 2002 redistricting, the Republicans picked up more new districts and lost fewer old districts than the Democrats. In addition, there are a number of districts (e.g. AR-1, AR-2, WV-1, TN-6, TN-8) that Republicans are almost certain to win this year that weren’t ever among the 285+ they had before. It seems conceivable that Republicans could pick up 70 or 80 seats this year, especially with them possibly beating 1994’s 7 point win. The high water mark, however, has been 232. That’d still be a healthy net of 53 seats.

The biggest reason the Democrats can lose so many seats this year is because they have 256 and they’d need another landslide to retain that many. Since the Democrats haven’t held a House majority with less than 50.9% of the votes, it’d be a complete anomaly if they retained the House with less than that.