Final answer:
The split of states between the two main political parties has led to changes in U.S. political party organization, including realignment and third-party influences on major parties. Critical elections have reshaped party coalitions, while increasing partisan polarization has reduced moderates, creating clearer distinctions between party platforms.
Step-by-step explanation:
The split of states between two political parties has led to significant changes in the organization of political parties in the United States. Political parties exist for the purpose of winning elections to influence public policy, building coalitions across a range of voters with similar preferences. The U.S. party system is a loose organization of fifty different state parties that have experienced several major changes since the Civil War. One of the critical changes is realignment, which occurs when significant numbers of voters switch their traditional party allegiances, reshaping the political landscape.
Throughout U.S. history, third-party movements have attempted to influence the direction of major political parties, though they have often served to divide party coalitions rather than establishing long-term success. However, these movements sometimes introduce important issues that are later absorbed by the two dominant parties. Critical elections have historically shifted the focus and organization of parties, while a trend toward increasing partisan polarization has emerged more recently, with parties diverging ideologically, resulting in fewer moderates in Congress and clearer distinctions between party platforms.
As demographics and societal issues evolved, parties realigned to maintain power. Party polarization has been particularly pronounced since the 1990s, causing the parties to compete more fiercely, resulting in a decrease in bipartisan cooperation. Ultimately, both the Democratic and Republican parties have reshaped their identities and constituencies in response to changes in the electorate and in the issues facing the nation.