Why the House and the Senate are moving in opposite directions

At first, I was a bit skeptical about the argument that Judge Brett Kavanaugh's confirmation process could lead the House and Senate in opposite directions. In general, in politics, a rising tide lifts all boats. Thus, no matter which party has benefited from the confirmation of the Supreme Court's candidacy, he should expect his fortune to improve in his best states and districts as well as in his worst.

But a split between the House and the Senate is exactly what we see in the Five Thirty-eight forecasts. Democratic prospects in the Senate are getting darker, falling to about 1 in 5. Indeed, it has been difficult to find good news for Democrats recently in polls in the Senate. In the House, on the other hand, their chances are relatively good. In fact, the Democrats' chance to take the House rose to about 4 out of 5, after slightly improving about 3 out of 4 immediately after Kavanaugh's confirmation. And while district-by-district electoral polls have been going on all over the place recently, the position of the Democrats has slightly improved compared to the congressional polls.

In appearance, you might think that the battlefields of the House and Senate are not this different from each other. Yes, this year's most competitive Senate races are in really, really red states. Specifically, the average Senate competition, weighted by its likelihood of being the deciding state in determining the majority in the FiveThirtyEight Tipping Point Index, is 16 percentage points more Republican than the country in its together. But the average competitive neighborhood of House is also pretty red: 8 points more Republican than the country as a whole, weighted by its probability of tipping.

The more time you spend watching the battlefields of each room, the more important conclusions you will make:

1. The battlefields of the House and Senate really are not that a lot. In many important ways, they are almost opposed to each other. For example, the battlefields of the House are more educated than the whole country, while those of the Senate are less so.
2. The map of Democrats in the House is quite robust because they do not depend excessively on a type of district. (This contrasts with the Senate, where most battlefields fall into a certain typology: red and rural). Although the House's battlefields are a little whiter, more suburban and more educated than the country as a whole, there are some exceptions, enough for Democrats to underperform in certain types of districts while having good chances to win. This position differs from Hillary Clinton's position in the constituency in 2016, in which the underperformance of just a group of voters in one region – white voters of the working class in the Midwest – was enough to cost him the election.

So let's take a closer look at the characteristics of the battlefields of the House and Senate, starting with some basic notions: their geographic area (according to the US Census Bureau) and whether they are races held by incumbents or free seats. In the series of graphs that follow, I will show what these features look like in an unweighted average of the 435 congressional districts, and compare that to what happens on the battlefields. (Rather than choosing "battleground" competitions, I weigh all races according to their odds of overthrow in the House and Senate, and competitions that are more likely to be decisive have a disproportionate influence in the calculation.)

An obvious but neglected difference between the House and the Senate is that Democratic incumbents have very little visibility in the House, but a ton in the Senate. For example, there is a 46% chance that the Senate race will be that of a Democratic outgoing candidate, but only 6% for the House. The reverse is true for Republicans; they have tons of vulnerable incumbents in the House, but few in the Senate. This means that, just like the other factors, the factors that reduce the advantage to the office of the occupying Speaker will tend to hurt the Democrats in the Senate, but will help them in the House. If, for example, the Kavanaugh hearings pushed the public more against the politicians in power of both parties, this could contribute to the growing divergence between the House and Senate forecasts.

Geographically, the competitive races in the House are almost evenly distributed among the four main regions of the Census Bureau. This is part of what makes the map of the Democrats sound: even if they have completely failed in one of these regions, they could still narrowly win the House by respecting the expectations of the model in the other three. Note however that, relative to the population, the South is slightly under-represented among the competitive districts of the House of Representatives: it accounts for 37% of all congressional districts, but 27% of the competitive districts. This is probably a good thing for Democrats because their coalitions in the South tend to rely on racial minorities and younger voters – groups that do not present as reliably at mid-term as they do in the South. presidential elections.

On the other hand, there is a 41% chance that the decisive threshold in the Senate will be in the South. And while the Northeast is pretty important for the house map, with a number of competitive races in New York, New Jersey and Pennsylvania, there's almost nothing interesting happening in the northeast of the Senate ledger.

Then, here are the political characteristics of the competitive districts, based on the FiveThirtyEight Lean Index and voted on in 2012 and 2016. (To make a comparison of apples apples between the House and the Senate, the statistics of Senate races in these next two graphs are based on congress districts in states with competitive Senate races rather than in all states. For example, if Tennessee is 11% likely to be the tipping point of the Senate, this chance is divided among the nine congressional districts of Tennessee to estimate the importance of each district in determining Senate control. )

It is true that the battlefields of the House are Republican tendencies, but that they are for the most part Republicans.leaning and not much more than that. For example, only 18% of competitive races in the House have a supporter bias of R + 10 or higher for the GOP. On the other hand, weighted by their importance for determining the outcome of the Senate, 63 percent Competitive districts are at least R + 10. The districts of Romney-Clinton and Obama-Trump, that is to say the districts that divided their vote between the last two presidential elections, are fairly important in the House, but not really in the Senate.

Finally, this is what competitive districts look like in terms of three increasingly predictive characteristics of electoral behavior: race, education, and urbanization.

I defined the districts where higher education is high and those where at least 35% of the adult population holds a bachelor's degree. According to this measure, 28% of the country's congress districts are highly educated. But 37% of the districts of the house on the battlefield are highly educated. In contrast, only 13% of the most important districts for Senate control have high levels of education.

At the racial level, the battlefields of the House and Senate are whiter than the country as a whole, but the asymmetry is more serious in the Senate: 38% of the most important districts for the control of the Senate are at least 80% white, not white, compared to only 23%. districts throughout the country.

Finally, House's competitive neighborhoods are concentrated in the suburbs and residential neighborhoods (defined by population density), which represent about half of the congressional districts but are close to two-thirds of the Chamber's competitive neighborhoods. The suburban and exurban neighborhoods are quite UNHowever, it is important for the Senate, where key races are disproportionately based on rural states or in states such as Nevada, where urban and rural areas mingle.

I will not go on too long because I hope these figures speak for themselves. I imagine that I had some idea of ​​the difference between the battlefields of the House and the Senate – but this intuition did not match the sharpness of the differences between the data.