The disparity between the political affiliations of America's professoriate and the wider population is, well, a bit more than statistically significant. Something like 90% of the faculty ID as Dems and/or liberals. But don't worry, it's not bias in hiring, it's just the natural outcome of what liberals and conservatives choose to do. Libs like learning and conservatives like money. Or something like that.
Righty-o. Suppose that women were pretty much on level with men in their secondary and college educational achievements and then suppose that there was, nonetheless, something like a 9-1 male-female faculty imbalance. Just what folks choose to do, right? Oh, wait, no, THAT's an occasion for numerous conferences, subsidies for women hires, and an almost obligatory sentence at the end of every job ad that women (as well as "minorities") are "especially encouraged to apply." But conservatives? They're just greedy or stupid or whatever. Righty-o, dude.
Now, I'm not much in the conspiracy business and while I have *no doubt* that there is a liberal hiring bias in the academy, that's not the whole story. I mean, you can be as crazy Marxist/postmodernist/whatever-the-left's-flavor-of-the-month-is as you want to be and you can still get hired just about anywhere. Write a dissertation defending traditional marriage as normatively preferable and see how many places drop that application into the "it'll be a cold day in Hades" pile. But it's also the case that the grad students who are earning PhDs tend to be liberal and that is itself, I think, a product of a self-perpetuating cycle. Smart students who think that maybe they'd like to be a prof look around and see that, well, most of the profs are liberals. This has, I think, a rather natural selective effect on conservative students, some of whom (perhaps rather reasonably) think that academia must not be for them. And so you get a winnowing-out process.
The biggest problem with that explanation is that it leaves untouched the original "liberalization" - why are the professors more liberal in the first place? Patrick Deneen, a prof at Georgetown, has what seems to me a pretty good answer: the changed nature of the university. Whereas the university used to be about (generally speaking) the preservation and transmission of knowledge and intellectual capacities, it is now about (generally speaking) about the production of research and promoting change in society. That is, the university has become the citadel of scientistic progressivism (e.g. we can "solve" any problem - and will solve any problem - merely by applying the proper scientific research techniques). There's not much of a place in the academia for conservatives of an older stripe, then, perhaps helping explain the wide disparities in political temperament and identification. Go read all of Deneen's post.