What if, as an experiment, we took two states that are comparable and simply declared one to be 100% Democratic and the other 100% Republican. Every person of the opposite party would have to move out of that state. The ex-patriots could simply go to the other state or wherever they want. Clearly, the state governments would do likewise and the governor, state senators, state house, mayors, US Senators and Reps ... would all be of the selected party. Any open seats would be filled by special elections.
So, these two states would get to be pseudo-independent from the rest of the United States. There would be trade and stuff but they would get to make any law they want, absolutely no holds barred.
These two states ... let's call them Democrance and Repulicongo ... would then just lead their lives, independently and eventually, whoever started the whole thing, would analyze the situation and see which form of government is the "best".
Which form of government, Democratic or Republican is the most successful. We could use a variety of rubric using measurements of "happiness" or "stress", various environmental parameters, economic strength, general quality of life, longevity, the arts, science, and so on.
This fantasy comes when a real-life Republican does something stupid and I say to myself, "Why don't they just leave the rest of us alone ... LITERALLY.
But, what states? We could use the idea that we take states that are already pretty far gone like Massachusetts and Louisiana or states that are close together like North and South Dakota. The similarities couldn't be demographic because of racial differences in politics but more like the distribution of cities and how arable the land is. We couldn't give the Republicans a state we don't want anyway and keep a really fun state. Well, why not just divide California ... no, that wouldn't work. We could use islands like Molokai and Lanai. I'm not sure it matters, anyway.
My point is that if the Republicans think they are so freaking smart then let them prove it. My bet is that as things move along, the young people of Republicongo want to immigrate to Democrance as they grow up.
Then, when it is clear that Democrance has worked and Republicongo is down the toilet and they come crawling back to us with their tails between their legs ... We could lock the door and throw away the key.