Please help me with my thought experiment concerning a multiparty United States.

When reality becomes disheartening, I, like many other people, turn to fantasies, counterfactuals, and other fictions.

One of my favorites is an alternate universe in which the United States is a multiparty parliamentary democracy.

They're also having an election right now, but it's a much more interesting one. Ron Paul, of course, is still in the running, with a large coalition of libertarians supporting him. There is a social conservative party, and there is a progressive party. Barack Obama is still establishing himself in national government (but where?), and John McCain is more of a marginal figure, because “mavericks” don't do as well in a parliament.

So here's the game, and this is where I need your help, since I am not exactly a “politics junkie”:

1.) What are the names of the parties, and who is the leader of each? (e.g. Social Conservatives, led by Sam Brownback.)

2.) What unlikely coalition might come to govern?

3.) Assume that there are real debates in this wonderful fantasy America. Which neglected issues would become important?

EXTRA CREDIT: How did this alternate USA come to have a parliament, anyway? (Please provide your answer in the form of a 400-600 page multigenerational epic with a comic touch: something like James Michener crossed with Michael Chabon.)