[Erax]

Having two-round elections takes care of the 'candidates A, B and C' situation. In the first round, everyone votes for the candidate they like best. The two most-voted candidates go on to the second round, then everyone votes again. Unless someone changed their mind between rounds, A gets all the votes he had before, plus some of C's votes. Same for B. Those who voted for C in the first round didn't throw away their votes, they are still getting to decide who gets elected. Candidate C's situation is not too bad either, as he can gain political capital by supporting A or B or neither in the second round.