@toby-pereira that's correct. And I believe that if this teaming is honest (the candidates are actually similar and don't want to spoil each other) then it is not the problem. Note that under standard (not spoiler-proof) voting rules, one of the candidates in the cycle could just quit the election, allowing the other candidate to win. We get rid of such strategic considerations here.
On the other hand, dishonest teaming shouldn't happen, since it is only profitable for the candidate who wins, not for the ones who lose nevertheless. Besides, in close battles, the very fact of dishonest teaming can outrage the voters (especially the supporters of the still losing candidate) and affect their preferences enough to change the whole situation.