Often unconsciously, says Cold Spring Shops
Consider, for example, the treatment of the Welfare Economics Paradigm in economics. It is easy enough to introduce market "failures" that "warrant" government corrective action. It is easy enough to design the optimal corrective action on a whiteboard. A student might easily leave a basic economics course with an understanding of economic policy that looks exactly like the Democratic Party talking points. The bias arises in the introduction of the "failure" and in the incomplete specification of "warrant." But to treat these topics properly takes time, more time than many basic courses permit, which often means these topics go only to upper-division economics students. A substantial proportion of the student body gets a vulgar and incomplete presentation of the Welfare Economics Paradigm.