The solution is to assume that anyone who gets power will act in a 100% corrupt, cynical, and self-serving way. It's a bit like building fault tolerance into a distributed system. Even if each of your servers will only be unreliable a very small percentage of the time, you must assume that at any given time, any given server could be down, or your whole system will be fragile.
Similarly, a government that relies on the moral character of its officials rather than institutionalized checks and balances is a weak and easily exploitable system of government.
If you have the checks and balances, you can still hope for politicians that will keep their promises, but when many of them inevitably don't, they will be limited in the amount of damage they can do.
That's right. The argument I often hear from people about the Snowden stuff is that, in contrast with a corporation, the government is there for "its people" and "will never abuse its power". What they forget is that the government is run by people, and people are by nature selfish and are looking for personal gain. So as you say, I think that "a government that relies on the moral character of its officials" is doomed to get corrupted and exploited, sooner or later.
Similarly, a government that relies on the moral character of its officials rather than institutionalized checks and balances is a weak and easily exploitable system of government.
If you have the checks and balances, you can still hope for politicians that will keep their promises, but when many of them inevitably don't, they will be limited in the amount of damage they can do.