In 1935, southern Democrats were given a fairly important exception to the expansion of the Fed's power over labor relations (which I think is probably the area in which they were the most uncomfortable with the New Deal). The Social Security Act of 1935 specifically excluded domestic workers and agricultural workers. Black southerners did this work, and the exclusion of domestic workers and farm workers simply does not make sense without this context (fyi: the SSA wrote a hilarious article trying to deny that this exclusion was racially motivated by drawing on some scant legislative history, but their argument is pretty weak and doesn't capture the Administrations frequent backroom dealing with Southern Dems, imo – check it out if you're interested).
This is the Ira Katznelson thesis from "When Affirmative Action Was White", which I remember doesn't hold up to scrutiny in this instance. Interesting review of the evidence for why domestic and agricultural workers were excluded from Social Security in this
article. It notes that about three times as many white workers were excluded as black, that there was no unified Southern opposition to the inclusion of agricultural and domestic workers, that every unemployment insurance scheme in Europe before 1935 excluded either or both categories of workers, and the architects of Social Security in the administration, inspired by those European programmes, were concerned with the administrative difficulties in covering informal workers like farm labourers and servants. For example it notes that Senator Tom Connally of Texas, who wiki says "led the opposition to federal anti-lynching legislation in the late 1930s, filibustering the Anti-Lynching Bill of 1937", actually advocated
for the inclusion of agricultural workers out of a concern that they would be excluded from the benefits.
Probably the most relevant passage to the general discussion about Southern Democrats and the New Deal:
Southern Democrats acted in concert against Northern Democrats only nine times between 1933 and 1949: five times to block anti-lynching legislation, twice against wage increases for the Works Progress Administration, once against an antidiscrimination provision in federal education financing, and once against a Fair Employment Practices measure. Southern Democrats failed to display their characteristic "solid" tendencies for the other 580 roll call votes (...) As a whole, southern legislators were more liberal than northerners between 1933 and 1937.* The one additional issue that tended to unite southern Democrats was the strong concern that federal funding should not be biased against their region.
