Final answer:
The initiative that led to the Democrat success at the national level was the creation of a new voting coalition that was diverse and focused on social welfare and civil rights, aligning with the interests of low socio-economic status voters in northern and midwestern cities. Despite internal divisions, particularly on the issue of civil rights, the Democrats managed to achieve national dominance by appealing to the electorate's desire for economic and social reforms.
Step-by-step explanation:
Democratic Success at the National Level
The initiative that led to the Democratic success at the national level involved building a new coalition of voters. This political shift began with the Democratic Party's efforts to appeal to a diverse group of low socio-economic status voters, particularly in northern and midwestern cities. These new Democratic voters were religiously and ethnically more diverse than the traditional, mostly White, mostly Protestant Republican supporters. The so-called 'Solid South', historically dominated by Democrats, agreed with the party on economic grounds but diverged on racial and social issues, maintaining a more conservative stance.
The alignment of the Democratic Party shifted substantially with the elections of Franklin Roosevelt, who managed to bring together various groups under the Democratic tent. The post-Depression politics focusing on supporting farmers and unemployment assistance worked to the party's advantage through the 1930s and 1940s. However, as social issues, particularly civil rights, became more salient in the 1950s and 1960s, fractures between northern and southern Democrats started to appear. Southern Democrats resisted the nationalization of social welfare and racial integration efforts, leading to a gradual shift of many towards the Republican Party, which endorsed smaller federal government and states' rights.
In essence, the Democratic Party's broadened base, support for civil rights, and the appeal to those seeking a change in the socio-economic system bolstered their national success.