The framers noted that the system was vulnerable to a single "faction" [1]. The solution was to have many competing factions. I think first-past-the-post, corporate election influence, and mass media consolidated power into a single faction that ended up causing the system to break down (in that the branches don't seem to be checking each other's power right now).
[1] https://en.wikipedia.org/wiki/Federalist_No._10