It's surprisingly hard to find a detailed by-major breakdown of these numbers. So far, the best I can do is this study based on a “national survey of 1643 (American) faculty members from 183 four-year colleges and universities” . (I haven't found one for the students.)
Ranking the departments by Liberal minus Conservative percentage margin gives:
- English Literature (85)
- Political Science (79)
- Theology/Religion (78)
- Psychology (76)
- Fine Arts (75)
- Philosophy (75)
- Performing Arts (68)
- Sociology (68)
- History (67)
- Music (66)
- Communications (61)
- Biology (58)
- Physics (55)
- Linguistics (54)
- Mathematics (52)
- Computer Science (48)
- Chemistry (35)
- Education (32)
- Engineering (32)
- Economics (16)
- Business (10)
- Nursing (6)
So, if this survey is representative, then all of academia is liberal, but the humanities departments are more liberal.