Along with increased turnout and massive support from- black voters in the South, recent Democratic wins in states like Virginia and Alabama came with the help of non-native whites who have relocated from the North.
According to the Washington Post, research by political scientists Sunshine Hillygus, Seth McKee, and McKenzie Young shows that white Americans who have moved to the South are less likely to be Republican than their native counterparts.
They draw this conclusion by looking at data going back to the 1970s from the American National Election Studies survey. Since 1968, the survey has asked respondents where they grew up. This allowed Hillygus and her colleagues to categorize white residents of Southern states as “natives” (people who grew up in the region) and “migrants” (people who grew up elsewhere). It’s important to note that their analysis focuses only on whites, so it cannot speak to the region’s growing diversity.
Migrants in the 1970s were more likely to be Republican, but that changed in the 1990s as the Democratic Party increasingly supported civil rights.
By the 2000s, that shifted again — and Southern migrants were more likely to be Democratic than their native counterparts. In other words, whites who weren’t born in the South were, on average, moving it to the left. The region’s most reliable Republicans were people who had grown up there.
The Post is sure to note that this is but one factor in today's Southern voter block, but it is one that seems to have benefited the Democratic Party.
Hillygus, McKee and Young suggest that population growth in the South may make left-leaning white migrants “an underappreciated component of a Democratic coalition that may be slowly reversing the electoral fortunes of a dominant southern Republican opposition.”