Reddit reviews Party Polarization in Congress

> First Past the Post is what has lead to the dichotomous relationship between the two parties,

No, safe districts did that. Before widespread safe districts the most conservative democrats and most liberal republicans overlapped each other. TLWR; Safe districts where only one party can win change the election from being two sides competing over as much of the whole voting population as possible to two candidates from a single side trying to out-flank each other by going further to their respective side.

If that doesn't quite make sense here's a more thorough explanation. Here's a graph of the entire voter base of any given area. There's the left, right, and the center.

{}D==========C==========R[]

A politician seeks election/reelection by getting 51% or more of potential votes. In a non-safe district either side has a reasonable possibility of getting elected, meaning the competition is between the Democrat and Republican candidate during the general election and the best path to victory is to capture the largest overall share of the population. The best way to do that is to capture as much of your side and the middle as possible. On a rough level the idea is that a Democrat (curly brackets) or Republican (square brackets) tries to get as much of the line (representing the voting public) inside their brackets as possible.

Here's an example of the Democrat candidate capturing less of the left but more of the center and even center-right votes, while the Republican captured more of the right but less of the center and no center-left:

{}D===={======C[===}======]=R[]


What happens if there's no chance in hell of the other side ever winning though? Instead of a Democrat and Republican competing by trying to combine their side with as much of the middle as possible it's now a Republican versus another Republican. Everything left of the midpoint no longer exists. So how do you increase your share of the vote? You capture more of the side you're on.

In this case two Republicans compete to see who can capture more of the Right wing voters... and the only way to do that is to go further right:

C={======[===}==========]R{}[]

Curly bracket Republican captured a lot of the center-right, but none of the left or center-left. Square bracket Republican captured less of the center-right but a lot more overall votes by going to the far right.

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Sorry if this is a little obtuse but reddit's format doesn't really work well for this sort of thing. If anyone wants I can throw together some shitty mspaint graphics to try and illustrate a bit more clearly.

Or if you've got time I really recommend seeing if your library/uni has Sean Theriault's Party Polarization In Congress. It's a very short and extremely accessible little booklet that goes over the history and development of party polarization and its main driving factors.