There doesn't need to be a special mechanism for power to corrupt; normal reinforcement learning should work perfectly well. When you're corrupt, you take actions to benefit yourself instead of those you're supposed to be benefiting. And if those actions do indeed benefit yourself, well, then, that's obviously the kind of thing that reinforcement learning is designed to teach you to do. You take the bribe, or set up a harem, or whatever, because being corrupt means that you are doing things that feel good to you (and are therefore reinforcing) instead of things that benefit the rest of the group.

It's easy to say you won't give into temptation when you've never been tempted before, but it's a lot harder to say that and also be right.