Game theory and history will tell you that third party candidacies just enable the most effective plurality to win. Bill Clinton won both his elections with a plurality, not a majority, in key states and there's a lot of evidence that Perot's candidacy is what he needed to win. Certainly, Carville and Clinton believed that since they supported Perot's candidacy and even fed Perot misinformation to blame some of their own dirty tricks on Bush and Dole.