David Greenberg in The Sixties, a Journal of History, Politics and Culture:
Scholars often ask whether the mainstream news media exhibit a liberal bias, but rarely where the idea of such a bias first came from. This article traces the idea’s origins to the civil rights movement. In the late 1950s and early 1960s, white Southerners grew resentful toward national journalists who covered the movement, whom they saw as advocating desegregation. Losing the battle for public opinion, Southern spokesmen such as Alabama Governor George Wallace adopted a populistic idiom, promoting the notion that an elite, left‐leaning Northeastern media were distorting the news to fit their politics – an idea that soon, under President Nixon, became conservative dogma.