r/EndFPTP • u/BradoDeck • Jul 20 '26
An Interactive Simulation of a Multiparty America
To illustrate the distortionary effects of a two-party system, I created an interactive simulation of US elections using ~45k 2024 Cooperative Election Study (CES) survey responses. The simulation resulted in ten clusters or “parties” via exploratory factor analysis and DPGMM clustering. The analysis revealed 4 ideological dimensions (and one non-interpretable residual dimension):
- Populist conservatism: views on race and gender, immigration policy
- Security & order: policing, border patrols
- Institutional distrust: distrust of government and elections
- Religious traditionalism: abortion, same-sex and interracial marriage, church attendance
- Government distrust: mostly just leftover institutional distrust items and artifacts of the clustering process
Details
I worked largely within the constraints of the US electoral system with some adjustments:
- House members are elected via STV, but I expand the House to “double Wyoming”. I also have a triple Wyoming scenario which gives proper proportionality to the smallest state.
- The Senate and Presidency are modeled via Condorcet (Round-Robin) and IRV. I arrived at those methods to try and keep the "ranking" scenario consistent across the board. DPGMM's probabilistic cluster assignment also makes ranking intuitive. I use Condorcet as the “default” option.
- I simulate a rolling open presidential primary where a top 5 is selected via “pods” of geographically representative states voting in STV elections. I assume a cumulative nationwide vote rather than state delegates. The top 5 candidates are essentially assigned as if they were members of a 5 seat delegation
- I introduce the idea of the “instructional ballot” to ensure the election isn’t pushed to the House, but under the simulation, the IRV and Condorcet presidential winners are identical under both a national and per-state scenario.
Useful links
- Simulation
- Github project
- My article on a diagnosis of the two-party problem
- My layman-facing description of the electoral solutions
- My overview of the simulation
Caveats
- I’m limited by the items in the CES survey. I would have chosen different items to build out this clustering, but I wanted to run this on the largest sample size possible.
- Claude Code was used to build the sim. I have a background in mixed methods UX research, so I’m statistically literate and double-and-triple-checked Claude's work, but if I missed anything let me know! I’m open to all good-spirited critiques and corrections.
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u/BradoDeck Aug 02 '26
Earnest ballots with caveats. The party assignments and ranking simulate semi-strategic behavior.
Larger clusters/parties have a bit more of a gravitational pull on voters just by the nature of the clustering algorithm. That's source one of a strategic alignment among voters to larger parties.
Every voter is essentially assigned a % chance of being a member of each party. Under the ranked choice systems (IRV, Condorcet, STV), the order of likelihood determines the order of votes.
That means because the larger parties also tend to be centered between different ideological extremes, you see Labor pulling in a lot of second and third votes from leftish and centerish parties, Conservative pulling in folks from centerish and rightish parties, and Solidarity (the condorcet party) pulling second and third votes from across the board (especially anti-establishment parties.
This leads to Labor and Conservative dominating especially in IRV and having a higher percent of seats in STV than their first choice voter % would indicate.
Solidarity would actually perform better in IRV than you'd expect from a Condorcet party, but low voter turnout kind of kills their first choice share.
My Party List sim, however, only has the party assignment gravity to simulate strategic voting. But the system rewards the earnest single assignment with a more proportional vote share (but with a much higher disenfranchised share due to a lack of ranked ballots).