narcoleptish wrote:I mostly see negatives.
Actually, there are some positives, and they make sense when you think about what our Founding Fathers intended. Our Constitutional system is designed to make change to our government slow. Their main fear was that the masses would go crazy during a crisis and try to drastically change the government in ways that they would never do if they were not in a crisis. So by guaranteeing that our government changes slowly we guarantee that we don't make too many rash decisions.
So the way that the two party system guarantees that is that it guarantees that our national campaigns stay moderate. In a three-party or four-party system you can have a case where neither moderate party gains a majority and they have to ally with extremist parties to form their government, and this pushes the government agenda in an extremist direction. The two party system, combined with the Electoral College, force our national political parties to appeal to moderates in purple states. They cannot just appeal to their base.
Just look at our recent presidential elections. As much as partisans tried to make it out like Good-vs-Evil epics, the candidates actually agreed on basically every issue. Obama and McCain both shot towards the center during their general election campaigns, to the point that the candidates were basically indistinguishable on every major issue. In general, this is a good thing. We will never have a lunatic president. Nobody can be elected without appealing to moderates in Ohio, Virginia and Florida.