Final answer:
Political parties globally have weakened since the 1960s with increased polarization in the U.S. and the rise of populist leaders internationally, signaling shifts in traditional alliances and voter behavior.
Step-by-step explanation:
Since the late 1960s, there has been a global trend of weakening political parties. The Democratic and Republican parties in the United States began to polarize, with the disappearance of moderates in the 1990s resulting in more ideologically homogeneous and adversarial parties. Internationally, countries like Venezuela and Indonesia have also experienced weakening party systems due to factors such as corruption, reduced party identification, and populist leaders. This trend reflects a shift in traditional party alliances and voter behavior, further challenging the efficacy of the party system in contemporary politics.