All kidding aside, I personally would prefer the parties to actually talk to each other and base their decisions on facts and actual debate instead of, essentially, flaming. However, that is the ideal world - a world we don't live in. At least we are not like the Japanese parliament where politicians occasionally come to blows, or the British parliament where they send occasionally clever insults at each other but, heck, that would at least be more fun to watch.
Either way, so far, the Republican party is the party that has veared farther away from centrist politics but now, there are factions on the left that want to have more of a say - vearing the Democrats farther left than they have been. I think that US politics would fare better if both parties remained closer to the center - where it seems that most US opinion lingers.