Update on the elections: the house distils the most (and the least) with the national mood

Welcome to our election newsletter on Thursday, September 6th!

After reaching a new record of 4 in 5 on Tuesday, the chances of the Democrats to win a majority in the House in our forecasts are a little folded on Earth. Recent national polls on generic ballots have been a little less optimistic for Democrats, and as a result, their chance to take control of the House has risen to 7 out of 9 (or 77%) in our "classic" model. .

Changes of a few percentage points are a fairly common occurrence for our forecasts. But not all districts are in phase, although the only new data available are national polls (as opposed to individual polls). This is because some districts are more "elastic" than others.

Nate Silver, editor of FiveThirtyEight, introduced the concept of an "elastic state" during the 2012 presidential campaign. The elasticity of a state is simply the sensitivity to changing the environment national policy. A highly elastic state is subject to great changes in voter preferences, while inelastic states do not blow as much with political winds.

An elastic state is not necessarily an oscillating state, or vice versa. Think of the difference between a state that is decided by one percentage point each election (a state of inelastic swing) and one that votes 10 points democratic one year and 10 points Republican the next (a state of elastic swing). In other words, elasticity helps us understand elections at a deeper level. Just knowing that these two districts are competitive does not tell you everything you need to know. For example, both call for different campaign strategies (participation in the first, persuasion in the second).

Today, we are delighted to unveil not only an updated elasticity score for each state, but also, for the first time, the elasticity scores of the 435 congressional districts! These results are from the 2016 version of the Congressional Co-op Study, a survey of more than 60,000 people conducted by Harvard University in collaboration with YouGov. The scores work by modeling the probability that an individual voter voted for the Democratic or Republican Congress, based on a series of characteristics related to their demographics (race, religion, etc.) and political (democrat). , republican, independent, liberal, conservative, etc.) identity. We then estimate how much this probability would change according to a change in the national political environment. The principle is that voters who are in the extreme – those who have close to 0% or 100% chance to vote for one of the parties, according to our analysis – do not change as much as those in the middle. .

You can download the data that our forecasts use to translate generic polls on the Congress vote into individual districts on GitHub via this link. However, the elasticity of each state (and the District of Columbia), as well as the first 25 and 25 districts of Congress (the highest scores are more elastic, the lower scores are lower).

Congratulations, 5th place in Michigan – you are the most resilient district of the US Congress! The district based in Flint and Saginaw has an elastic score of 1.24, which means that for every percentage point the national political mood is moving towards a party, the 5th district should move 1.24 percentage point to this party. In practice, this means that district votes differ from year to year and even during elections. For example, in 2016, he voted for Hillary Clinton for president 50% to 45%, according to Daily Kos Elections, but Democratic Representative Daniel Kildee for Congress 61% to 35%. In the top 25 are also six districts of Massachusetts and one of Maine, New Hampshire and Rhode Island.

As a rule, the most vibrant neighborhoods tend to be those with a lot of white voters who do not identify as evangelical Christians. (By contrast, white evangelical voters are predominantly Republicans, while non-white voters – with a few exceptions, South American Cuban-Americans, note the presence of the 25th and 26th districts of Florida in the top 10 – are largely democratic in the Northeast and Upper Midwest, where they were vital to President Trump's winning states such as Ohio and districts such as the 2nd Congressional District of Maine.

At the other end of the spectrum, the 3rd district of Pennsylvania, which covers downtown Philadelphia, is the most inelastic district of the country. This makes sense, given that it is predominantly African-American, a group that systematically votes for Democrats at rates of about 90%. Seven other majority districts in New York are also in the top 25. Two of the last 10 are in Alabama, where most voters are African-American (democratically reliable) or white evangelical (Republican), making them very inelastic. .

The list illustrates what I have previously noted: competitive districts can be elastic or inelastic, and elastic districts can be competitive or non-competitive. For example, the 1st district of Massachusetts is quite elastic (1.22), but it is not very close to Democrats and Republicans (according to the partisan metric of FiveThirtyEight, it is 27 points more than the country ). between slightly blue and super blue. And there are competitive districts in the elastic range: the 4th Nevada district (rated "probably D" by our classic model) has a 1.22 elastic score, the 3rd district of Iowa ("Lean D ") The 7th District of Georgia (" Lean R ") has a score of 0.85.

Keep these numbers in mind during the 2018 campaign. At this moment, the Democrat Steven Horsford is the favorite of the 5 in 6 in Nevada, but if the national environment is favorable to the Democrats, the Republican Cresent Hardy could be quickly because the district is so elastic. On the other hand, Democrat Carolyn Bourdeaux, 7th in Georgia, who is 3 out of 10, will probably have to count on a voter turnout, in addition to a good national environment, because this district is so inelastic.