What is the 'party decline thesis' regarding U.S. political parties?

The party decline thesis suggests that political parties in the United States have experienced a significant weakening of their influence and organizational strength since the 1950s. This concept is rooted in various factors, including the rise of individualism in politics, increased voter engagement in issues outside the traditional party structures, and the advent of new forms of communication and campaigning that diminish the role of parties in mobilizing or controlling the electoral process.

Scholars argue that this decline is marked by a decrease in party identification among voters, with more individuals identifying as independents rather than aligning with a specific party. Additionally, the influence of interest groups, social movements, and increased access to information through the internet and social media has empowered individuals and marginalized the role of parties in shaping political discourse and mobilizing the electorate. Overall, the party decline thesis provides a framework for understanding the transformation of the U.S. political landscape and the shifting dynamics of voter behavior and party function over the last several decades.