Final answer:
Minor parties often play what is known as a spoiler role in elections by attracting votes from disaffected constituents of major parties, potentially altering the election's outcome in favor of the party least preferred by the voters who defect to the minor party.
Step-by-step explanation:
Minor parties can play a decisive role in an election by pulling votes from one of the major parties, and this is often referred to as a spoiler role. This phenomenon occurs because third parties can attract votes from people who are dissatisfied with the major parties. Notably, a minor party acting as a spoiler can change the outcome of an election, as seen in cases like the 2000 Bush v. Gore election where Ralph Nader's candidacy and the Green Party drew votes away from Al Gore. Third parties also serve as safety valves for political discontent and can introduce important issues into the public discourse, pushing major parties to absorb these issues into their agendas over time. Despite the challenges they pose, third parties fulfil a legitimate part of the electoral process by providing voters with more options and highlighting specific issues like the environment (Green Party), even though they seldom win office due to the nature of the majoritarian electoral system.