The main elements of the shift are that the Democratic Party built, under FDR, a coalition that could and does viably win national and state and local elections while before him, it could only do so in cases like Grover Cleveland and Wilson where the Republicans were infighting to a point a Dem could sneak in through the back door. Both parties had liberal and conservative wings. The Taft Republicans were the prototype of today's conservative Republicans, Roosevelt's wing fell apart by the Reagan era and has been dead for a long time as of the 2000 election.

The Democratic Party went from a sectional and state party that occasionally won national elections to a national party based on a coalition of marginalized groups and Black people starting to switch from GOP to Dem under the Coolidge Administration and Harding Administration. The biggest cause of the switch was Republicans having a majority in Congress and refusing to address lynching, at the time.