When did third political parties have the greatest influence on the nation?

Third political parties had the greatest influence on the nation during key historical moments, particularly in the late 19th and early 20th centuries. The Populist Party in the 1890s challenged the two-party system by advocating for farmers' rights and economic reforms. Similarly, the Progressive Party in the early 1900s, led by figures like Theodore Roosevelt, pushed for social reforms and greater government intervention, shaping national policies. These movements often forced the major parties to adopt new ideas and address issues they might have otherwise ignored.