I'm not saying God "did this", but nothing happens outside of God's plan and purpose. He knows the end from the beginning. Even though we have free will, there is nothing we do that surprises Him or that can somehow foul up His plan. It's a mystery. And you are right, WE the people have the leaders we elect (at least that's supposed to be how it works), but even this fits into His plan and we have to trust Him. I've been praying for months for Obama to lose, but he didn't, so either God doesn't hear our prayers, He doesn't care about what we bring to Him in prayer or He DID hear and He DID answer our prayer. I prayed for God's will to be done, so I trust that it WILL be. Obama might be able to steal an election but he cannot steal my hope.
Why isn’t God enslaved, so to speak, by His own omnipotence? That’s a philosophical question. But it matters. We have to be able to speak of God permitting things that in some manner He does not want or does not prefer, in order to have a world in which evil is even possible without said evil being endorsed by God. God has to allow His handiwork to resist Him without causing it to happen. It falls into the realm of miracle.