Final answer:
Third parties have influenced American politics by raising specific issues, providing alternative choices to voters, and potentially altering election outcomes.
Step-by-step explanation:
One of the main ways third parties have influenced American politics is by raising specific issues that are important to the mainstream public but may be ignored by the major parties. Third parties provide voters with more alternatives than just the two major parties, and their presence can significantly alter the outcome of an election. By taking votes away from one of the major parties, third parties can act as a “spoiler” and cause the other party to win.