Final answer:
The civil rights movement and social issues of the 1960s, including differing views on states' rights and social welfare, caused many Southern Democrats to switch to the Republican Party. This culminated during the 1980 presidential election with the 'Reagan Revolution,' which marked a significant realignment in American political affiliations.
Step-by-step explanation:
In the 1960s, a significant issue dividing the Democratic Party was the civil rights movement. Many Southern Democrats who had been part of a Democratic alliance with Northern Democrats on economic issues began to dissent from the party's growing support for racial equality and civil rights. This ideological rift concerning social issues like civil rights for African Americans, along with differing views on states' rights and social welfare, led to many Southerners transitioning from the Democratic to the Republican Party.
The shift was significant during the 1980 presidential election, which is often noted for the 'Reagan Revolution,' where Ronald Reagan attracted conservative Democrats with his emphasis on smaller government and greater states' rights. This realignment was further solidified as the evangelical movement gained political influence, steering its constituency toward the Republican Party.
By the 1970s and 80s, this shift had cemented a new political landscape where the North and West favored Democrats, while the Solid South turned Republican, a stark contrast to the post-Civil War allegiances.