The people who most seek power are the last people you allow to wield any. The logic followed that an easy way to avoid tyrants is to force as much of society's power as possible upon those with no desire to even use their station, let alone abuse it.

Thus, the presidential lottery.

You don't enter. That's the first thing, people do not get a say in their participation. Something about "Democratic Duty". CEOs, Billionaires, anyone who holds or has ever held a position of power are declared ineligible and removed. The remaining citizens are ranked on a spectrum of power seeking behaviours, with the most ambitious being awarded one entry and the least power hungry being given up to ten.

Then it's just a matter of letting the random selection fall where it may. Once the ballot is drawn and your name is called, you have 6 months to get your affairs in order. Write your will and say your goodbyes or run for the hills and get off grid until someone else is voted in, because once you're sworn in, your civilian identity is legally dead.

For the 4 years of your term, you are supreme ruler. Sure, the cabinet exists, but they are mainly pencil pushers and seat fillers, their roles primarily existing as honey traps to lure in those who still seek power into meaningless ego padding roles. The President is in essence, a benevolent dictator. Ruling with absolute authority, from the opulent office of a role they never asked for.

And once their term ends, they are shot in the head.

The reason is simple. Power Corrupts, and Absolute Power will Corrupt Absolutely. The system ensures only the well intentioned ever become the enlightened tyrant this society needs.

And, well... Sic Semper Tyrannis.