Final answer:
The decline in party competition since 1972 has been influenced by increased polarization and a reduction in moderates, leading to less bipartisan cooperation and altering state electoral dynamics.
Step-by-step explanation:
When examining the decline in party competition since 1972, it's evident that the factors contributing to this trend span various dimensions, such as societal changes, economic shifts, and political dynamics. In the U.S., this decline in party competition can be characterized by the rising polarization of political parties, with moderates becoming less common and both parties shifting further from the center.
The shift has led to decreased bipartisanship, increasing the difficulty of passing legislation and impacting political dynamics within states. Based on the provided context, while the text does not explicitly mention which state(s) have seen the greatest decline in party competition, the overall implication is that Republican and Democratic parties have become more ideologically homogeneous and polarized, altering the effectiveness of third parties and changing the electoral landscape.