Final answer:
The Civil War led to an increase in popularity for the Democratic Party due to the shifting perception of Republicans as the party that had freed the enslaved, the support from labor union members and immigrants who viewed African Americans as competitors, and the Democratic Party's support for civil rights and social welfare policies.
Step-by-step explanation:
The Civil War led to an increase in popularity for the Democratic Party for several reasons. First, after the war, Republicans, the party of Lincoln, were viewed as the party that had freed the enslaved. Their efforts to provide Black people with greater legal rights earned them the support of African Americans in both the South and the Northeast. This loss of support for Republicans in the South allowed Democrats, the party of the Confederacy, to regain control of the region.
Second, Democrats in the North and Midwest drew support from labor union members and immigrants who viewed African Americans as competitors for jobs and resources. They opposed giving African Americans equal rights and saw the Democratic Party as representing their interests.
Lastly, in more recent times, the Democratic Party has supported civil rights and social welfare policies, which gained popularity among African Americans and caused a shift in support from the Republican Party to the Democratic Party.