but not a realistic operational one. The system is now set up for two competing parties, and the spectrum has a left and right end. Too many parties and it becomes unstable. Two parties and you always have a contest, even if it occasionally, and temporarily, becomes one-sided. Even with a multiple party parliamentary system, you usually wind up with two coalitions, one on the R and one on the L.

Ideology probably has a lot less to do with it than we think. It's just business, with the Us vs Them schtick thrown in to keep the fans happy. Think of football, its not the teams that matter, its the Sport. Do you think the Commissioners care who wins the Series? In fact, a friend of mine who works in the Beltway bureaucracy once described Washington politics to me as "pro wrestling for college graduates". This is why the real pros, like Carville and Matalin, often wind up in bed together.