Final answer:
The Republicans became more popular during the Reagan era in the 1980s, primarily due to ideological shifts on social issues and the appeal of smaller government and states' rights that won over many former Democrats. The correct option is B.
Step-by-step explanation:
During the Reagan era, which political side grew more popular in the 1980s? The answer is b) Republicans. This growth in popularity stemmed from several sociopolitical developments throughout the 1970s and 1980s.
Due to shifting ideologies on social issues, traditional Southern Democrats began migrating towards the Republican Party, particularly during the 1980 presidential election where Ronald Reagan's appeal to conservative values, states' rights, and smaller government resonated with many former Democrats.
This phenomenon, often referred to as the 'Reagan Revolution,' marked a significant realignment in American politics. In this period, polarization in Congress increased, leaving little room for moderates and facilitating the rise of a more ideologically conservative Republican Party and a more liberal Democratic Party.