Not to hijack the thread but -- (and echoing VoodooEconomist to a small extent)
sometimes there are subjects too close to the current and you'd have zealots and trolls out to make their ideology either the feature or the martyr of the game.
I like your overall concept but there are also other periods in history (with distance) that gives a better perspective to building a game that the demagogues wouldn't flock toward.
Given the putrid level of current political discourse in my country, I am of the 'plague on all their houses' mindset and would never buy a game that simulated the winner take all bull crap mindset of the modern day. AND linking economics to political parties would involve some programming in of the favorites creating a game of biases and opinions, not a real simulator.
Much more entertaining, educational and challenging would be to create the Elector's system of the HRE and track that 200+ year period of time. Think of it as a cross between Vicki (lite) and CK2 (lite). Yes, Euro-centric and a bit obscure to the North American audience a political character driven game with a strategic economic and military model to play might make some money.
Another extremely interesting (and distant) political themed game could be controlling the Papacy from 1400-1600 with Italy as the actual battle map, but the big countries playing their card(inal)s to keep the Pope on their side in other (political/option/off board) disputes. As a basis of this game I refer to an old Avalon Hill board game called 'Machiavelli'.
I agree, a political (which is still - character driven) game could be fun, but a bit of distance from the Repub-o-tard/Dummy-crat ghastly boring horror show going on currently might attract more customers. I, for one, would not buy a modern political simulator.