There’s a reasonably — but only reasonably — interesting debate about this question at the Economist. I don’t find any of the arguments especially convincing but I’m glad that people are openly asking this question in a conservative magazine.
Personally, I would argue that that the Republican party and the permanent government (think tanks, media elites, etc.) are clearly broken, while the Democratic party is only, at worst, marginally more dysfunctional than it has historically been. Over all, that makes for a broken system.