During the "Shoot Em In The Head" side quest in the Republic of Dave, win the Speech challenges to receive the key and be allowed to stay. Ask Dave if there is anything to do to help with the elections. He will tell you to get everyone to vote. Go to Bob and Rosie and get them to run for President and get everyone to vote. Inform Dave you are finished, then run to the ballot box and hide behind it. It is locked but keep pressing on it until Dave comes to open it. You will see the ballots and can now rig the election.