-Allow for voting for null. If null wins, position goes unfulfilled. Belgium did it for the longest time. Nothing broke in thr meantime.
-Make it costly to bribe. All voting positions are subject to a random swap. For example the winner of a senate seat in FL is forced to swap for state assemblyman. If declined, the runner up takes the spot. And this is true for all elections including president.
-Get people to fight about insignificant topics. In switzerland, people argue at the canton level about the size of the local roads. No oxygen left to argue national, topdown issues. This can be achieved by bringing direct democracy rules (similar to suisse) into USA.
I think all 3 could pass on a nationwide referendum with a powerful enough executive.