Final answer:
During the Second Party System, the Democrats and Whigs were the two main competitive political parties. They engaged in significant political rivalry, influencing the political dynamics and policies of the era.
Step-by-step explanation:
The two most competitive political parties during the Second Party System were the Democrats and the Whigs. This period was characterized by significant rivalry and debate between these two parties, as they vied for political control and influence over public policy in the United States. The Second Party System played a crucial role in shaping the political landscape of the era and established patterns of party competition that mirrored the dynamics of later party systems, including the contemporary dominance of Democrats and Republicans. While third parties such as the Green Party and Libertarian Party exist today, the Second Party System was primarily defined by the intense competition between the two major parties of that time.