They should be stood against the wall and shot. There is no greater crime than election tampering.
Ten or Twelve shot double voters would bring the practice to a grinding halt.
“double vote - double tap”
They have a particular punishment in Singapore called caning that might be more suitable for this crime than a firing squad. It’s pretty brutal punishment,but I don’t think it’s ever killed anyone. Doing nothing to those found guilty of this crime sure isn’t the answer,except to allow the spread of the problem. There should be suitable punishment for those who advocate voter/election fraud as well.