Final answer:
The social movements of the 60s and 70s caused a major realignment in the U.S. political parties, with many Southern Democrats moving to the Republican Party over issues of states' rights and social norms. This shift contributed to increased polarization in American politics and had lasting effects on domestic and foreign policy.
Step-by-step explanation:
The social movements of the 1960s and 1970s had significant impacts on the national political parties in the United States. The Democratic Party experienced a realignment as social issues such as civil rights became central to its platform, drawing in a more progressive base from the North and West, but alienating many Southern Democrats who favored states' rights and opposed federal interventions in social policy. These Southern Democrats began shifting their allegiance to the Republican Party, which further polarized the parties.
The Republican Party championed smaller government and states' rights, attracting disaffected Democrats. This realignment was epitomized during the 1980 presidential election when evangelical voters moved their support from Jimmy Carter to Ronald Reagan, solidifying the conservative shift within the Republican Party. Additionally, foreign policy, particularly the Vietnam War, influenced voter perceptions and party affiliations by creating a surge in conservatism that prioritized traditional values and criticized social movements.
By the 1980s and going into the 1990s, both political parties became more ideologically polarized. Moderate Republicans and Democrats who had historically worked together on issues like racial equality and economic policy were supplanted by more ideologically driven legislators, reducing bipartisan cooperation and increasing partisan divides on both the domestic and foreign policy fronts.