Generic Ballot for Congress

[pbrower2a]

We are now less than a year away from deciding what sort of Congress we shall have in 2018. Nate Silver has some topical analysis.

Democrats have a marked edge in the Congressional ballot -- nearly 10% at times. That is huge. Are Re0publicans likely to reduce that margin significantly?


(Nate Silver, at 538.com)

Quote:The generic congressional ballot, even more than a year before a midterm, has historically been quite predictive of what will eventually occur in the following year. It was predictive in April, and it’s even more predictive now. You can see this phenomenon in the chart below. The chart shows the margin by which the presidential party leads on the generic ballot in an average of polls in October1 a year before the midterm compared with the national House margin in the midterm election. Every midterm cycle since 1938 is included, with the exception of 1942 and 1990, for which we don’t have polling at this point in the cycle.



The generic ballot polls a year from the election and the eventual House results are strongly correlated (+0.90). Importantly, past elections suggest that any big movement on the generic ballot from this point to the midterm tends to go against the president’s party.2 That movement explains why the Democrats lost ground in 2010 and 2014 in the generic ballot polls when they controlled the White House, while they maintained their lead in 2006 when Republicans held the White House. (With a similar set of data, I used the generic ballot to forecast Democratic problems early on in the 2010 cycle.)

Indeed, recent election outcomes show that Republicans should be worried about what the generic ballot is showing. The results in Tuesday’s gubernatorial races in Virginia and New Jersey were called perfectly by the generic ballot once we control for the partisan lean of each state. The special election results this year have also been in line with a big Democratic lead on the generic ballot.

https://fivethirtyeight.com/features/the...-from-now/