Which constitutional arrangement BEST prevents the abuse of governmental power by ensuring that no single organ of government dominates the others?

The doctrine of separation of powers divides governmental authority among the legislature, executive, and judiciary. When combined with checks and balances, each arm is given the ability to monitor and restrain the others, preventing any one branch from accumulating excessive power. Federalism distributes power territorially but does not by itself prevent domination among the three arms of government.