What will turnover in the House be?

Far off in the hinterlands of neglected contracts and forgotten offers lies this hidden midterm market: How many U.S. Representatives will begin their “freshman” term in Jan. 2019?

The Rules

We begin, as we always should, with The Rules.

At the beginning of the 116th Congress, the number of U.S. Representatives who were not U.S. Representatives at the close of the 115th Congress shall be the number or range identified in the question. Earlier service as a U.S. Representative will not disqualify a member from being counted toward resolution of this market.

Straightforward enough – of those who are there at the beginning of the 116th, how many were not there at the end of the 115th?

What to figure out

Clearly we’re going to want to know two categories of Congresscritters:

(1) Those that have already confirmed they are retiring, and will therefore not be a part of the 116th plus those who have already retired and whose seat remains vacant or is otherwise guaranteed to belong to a new face;


(2) Those who are at risk of losing their seats in the upcoming elections.

The Baseline

The number in category (1) gives us our baseline – we cannot have less turnover than this number.  So let’s start there:

With a little help from the friendly analysts over at 538, we can see that there are 23 Republicans retiring from the House alongside 8 Democrats.  But wait a minute!  Those are just “pure” retirements.  There’s a whole ‘nother category of those who are leaving because they’re running for higher office (for instance, see this list from The Atlantic).  So let me spare you the work (as is the purpose of this blog) and just tell you that there are at absolute minimum 57 districts that will have new representatives in the 116th Congress.  (Check my work here).

(Note: I may have gotten something wrong in Pennsylvania because that whole thing is a mess.  Also though it doesn’t seem likely anymore, the NC redistricting case could have flipped the script here as well.)

So how many seats need to flip?

Well that depends on what bracket you want to win, of course 🙂

But let’s dive into category (2) by considering the case of the last contract on the board, 85 or more.  Here we need at least 28 incumbents to get knocked off.  That means we need to find 28 competitive districts in which an incumbent is running, and hopefully a lot more since presumably some fraction will survive.  To get this list, I’ll go by the modelers at 538 and take all the districts that are somewhere between ~25% and ~75% for the incumbent.  This will let us break down the possible incumbent dethronings by likelihood.

Long story short, there are 42 districts that 538’s model has between 25% and 75% chance of the incumbent running; all are held by Republicans.  By likelihood:

  • 17 are less likely, with odds ranging from about 25% to 40%
  • 12 are coinflip-ish, with odds ranging from 40% to 60%
  • 13 are more likely, with odds ranging from 60% to 75%

Um, okay?  Cool?

Right, right.  Where does this leave us?  Well basically to get to 85 or more you need a real Blue Wave.  They need to be running the table in their likely un-seatings and taking most of their coinflips along with a probably a few of the stretches.  Your mission – should you choose to accept it – is to determine how likely such an event is.


Disclaimer: I probably have positions or intend to take positions in just about all the markets I discuss herein.  You should always do your own research prior to making any investment decision. You should consider my advice and knowledge I share to be fundamentally biased in its presentation and selection by my own financial incentives.  While I do not knowingly lie I certainly do knowingly omit information that I think gives me an edge.

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