Final answer:
The two-party system in America is a result of winner-take-all electoral rules, historical party evolution, and the perceived lack of viability of third parties. Voters support major parties to back potential winners, while major parties have advantages that make it difficult for third parties to succeed.
Step-by-step explanation:
The two-party system in America is primarily due to the winner-take-all electoral rules and the historical evolution of political parties based on ideological positions and constituents. Most voters understand that minor parties have no real chance of winning, so they tend to vote for candidates of the two major parties in order to support a potential winner. Additionally, the major parties have advantages such as automatic ballot access, making it difficult for third parties to be successful.