Democrats are always eager to explain away the past dark periods of their party by explaining how the parties flipped. Post Civil War, blacks supported the Party of Lincoln, the Republican Party. Democrats may have been forced to surrender slavery, but they imposed Jim Crow as soon as Reconstruction ended. This continued for decades, especially since the Republicans held dominance in the government from 1861 until 1913. In 1913, Woodrow Wilson was inaugurated president and reintroduced segregation in federal workplaces. He was an apologist for the South and screened Birth of a Nation at the White House. However, when FDR was elected in 1932, he retained segregation. In 1948, Harry Truman desegrated the military. In 1954, during the presidency of Dwight Eisenhower, the Supreme Court overturned the policy of 'separate but equal.' Eisenhower set about enforcing this with the National Guard and pushing both the 1957 and 1960 Civil Rights Acts.
By the time JFK arrived in office, the writing was on the wall for segregation. It was doomed and any Democrat with sense was going to abandon it. Where Republicans had argued to just treat blacks like everyone else, Democrats embraced a strategy of one-upmanship. Not only would they pass the 1964 Civil Rights Act (with strong bipartisan support), but they would also implement affirmative action. Though a noble goal, it assumed employers were guilty of discrimination if the pool of employees did not match local demographics. So, the Democrats went from discriminating against blacks to now discriminating in their favor. Low grade reparations? Though Republicans continued with the same old policy of just treat everyone the same, that now meant repealing quotas. That's anti-black! Sigh.
The Democrats have spent decades claiming that Republicans are holding blacks back and yet, most blacks live in cities that have been governed by Democrats for all those decades. For instance, Detroit hasn't had a Republican mayor since 1962. Whose fault is the decline of that city? What about St. Louis? Last Republican mayor left in 1949. Philadelphia? Last Republican mayor left in 1952. The modern Democrats are the same as the old Democrats, they have just changed their tactics. The Democrats have trapped blacks in a new kind of plantation - harvesting their votes during election season by blaming the Republicans for their misery.