[ES: I am not a political scientist. I’ve tried to find good political science on these topics and failed; maybe you can point me in the right direc

Secrets Of The Median Voter Theorem - by Scott Alexander

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2024-10-25 06:30:02

[ES: I am not a political scientist. I’ve tried to find good political science on these topics and failed; maybe you can point me in the right direction]

The Median Voter Theorem says that, given some reasonable assumptions, the candidate closest to the beliefs of the median voter will win. So if candidates are rational, they’ll all end up at the same place on a one-dimensional political spectrum: the exact center.

Here’s a simple argument for why this should be true: suppose the Democrats wisely choose a centrist platform, but the Republicans foolishly veer far-right:

Now suppose that every voter (represented as a point on this line from furthest-left to furthest-right) reasonably chooses the candidate closest to their own position:

The real median voter theorem is much more complicated than this, and can handle arbitrary numbers of candidates and complex voting methods. But this argument is good enough for now.

Elegant as this proof may be, it fails to describe the real world. Democrats and Republicans don’t have platforms exactly identical to each other and to the exact most centrist American. Instead, Democrats are often pretty far left, and Republicans pretty far right. What’s going on? I think at least three things.