Final answer:
Single-issue parties tend to be short-lived because they focus on specific controversial issues or narrow causes, limiting their appeal among the electorate. These parties often lack the support needed to win elections and face obstacles in a system dominated by two major parties.
Step-by-step explanation:
Single-issue parties tend to be short-lived because they often focus on a specific controversial issue or a narrow set of causes, which limits their appeal and support among the electorate. These parties may attract a small percentage of voters, but they will always lose to more popular parties in a system where individual candidates compete for individual seats. As a result, their supporters realize they have no hope of achieving success at the polls and may eventually abandon the party. Additionally, forming a third party in the United States is challenging due to winner-take-all elections and the dominance of the two major parties, making it difficult for single-issue parties to gain wide-reaching influence.