It will still catch every one else.
To prevent a corrupt agency from coming to power, you need checks and balances. Give a different agency surveilance authority and a different agency security responsibility.
Have law enforcement trained on election laws and observing elections in highly contested areas. Make sure the laws have penalties. And that officers are willing to make arrests.
The left has plenty of officers willing to make arrests even worse they have about half the population willing to snitch on their neighbors.