I wouldn't say that Phillips has switched sides. In fact there seems nothing in the class analysis that demands that you take one side against another. Marx made this point when invited (in a letter to Kugelman, I think) to say what was novel in his approach.
from memory, he says something like 'no credit is due to me for the analysis of class' arguing that this was common to political economy (he meant Ricardo) and historical research before him. (Rather he says that what was novel to him was the understanding that class struggle culminated in the abolition of class society).
Kevin Phillips 1969 bible of Nixonism, 'The Emerging Republican Majority' is also a class-based analysis: it takes the white working class as its subject, and counterposes them to what would later be called the black underclass.
-- James Heartfield