To partly copy an earlier post I made about black-white coalitions in the South.
Republican-Populist coalitions surged to power across the South in the 1880's and 1890's. North Carolina was governed by such a coalition from 1894-1900. You also had the Readjusters in Virginia. The peak of black political representation wasn't in 1876 (when Reconstruction ended), but actually the late 1880's.
The widespread fear among upper-middle-class white Southerners that other such governments would form elsewhere was one of the primary motivations for Jim Crow - which effectively disenfranchised almost all blacks and a significant share of poor whites. There's a common notion that elite planters made this happening by appealing to poor whites through white supremacy, but that I think is wrong - it was very much fear of a coalition of poor whites with blacks that caused upper-middle class whites to bring along the elite planters by embracing a much more radical form of white supremacy. In many cases, upper-middle-class white Southerners (for example, like Ben Tillman) were more radical white supremacists than the traditional Southern planter elites they joined with (for example, like Wade Hampton).
This was very much the context in which Martin Luther King, Jr. grew up in - and he specifically cited C. Vann Woodward's description of this phenomenon to explain to people why he did not believe Jim Crow could not be defended as an inherent foundational part of "Southern culture," as many of its apologists (and I suppose a lot of glib modern columnists who want to dunk on the "wrong kind" of white people) claimed. It also explains why Martin Luther King, Jr. was a socialist who was so avid on forging a coalition between poor whites and poor blacks (the Poor People's Campaign), before he was more or less assassinated by a white supremacist terrorist (again, a very common fate for people trying to establish such coalitions - a violent coup more or less brought an end to the biracial North Carolina government.)
There's this really destructive modern US tendency to treat historic white supremacy as this cultural-racial kind of original sin inherent in all whites, neglecting all of the economic antecedents. For some bizarre reason, sometimes people call this narrative "cultural Marxism", when it's literally the opposite of Marxism.
Basically, to get poor whites and blacks to band together into a socialist majority, you need to butterfly out Jim Crow. How do you do that? Well, one of the most fascinating things pointed out by Woodward was that Jim Crow did not emerge in an ideological vacuum. It was openly aided, abetted, and supported by Northerners who grew to more or less embrace racist anti-black attitudes and thus support Jim Crow. This era was the height of scientific racism. Jim Crow could have never happened if say, the Supreme Court hadn't
unanimously greenlit Mississippi's 1890 Constitution, which disenfranchised both whites and poor blacks. Similarly, the most ardent supporters of Jim Crow weren't poor whites - they were middle-class whites, who loathed poor blacks and feared poor whites.
The way to make the United States South socialist is quite easy - get the rest of the country to go socialist. Because if you've changed things enough to make the North go socialist, you've also probably changed enough things to make the South socialist.
That being said, it's not all unheard of for the overwhelming share of poor whites and blacks to be in the same political coalition. This was accomplished in 1976, when Jimmy Carter more or less tied Ford among Southern whites (thus winning the vast majority of poor Southern whites, as he lost affluent Southern whites very badly) while also winning a large majority among black voters. And Jimmy Carter was obviously no segregationist.
If anything, poor Southern whites and black voters both voting for the same candidate appears to have been the American norm until, well, 2016. For an illustration of this, look at poor, almost entirely white
Elliot County, Kentucky, where Lyndon Baines Johnson trounced Barry Goldwater, a stunning 86.2-13.7%. Even George McGovern won by over 30 points, with Bill Clinton winning by 45 points, Kerry winning by 40, and Obama by 25. And then fast forward to 2016, with Trump winning by 45 points.
