But contrary to conservative rhetoric, studies show that going to college does not make students substantially more liberal. The political scientist Mack Mariani and the higher education researcher Gordon Hewitt analyzed changes in student political attitudes between their freshman and senior years at 38 colleges and universities from 1999 to 2003. They found that on average, students shifted somewhat to the left — but that these changes were in line with shifts experienced by most Americans between the ages of 18 and 24 during the same period of time. In addition, they found that students were no more likely to move left at schools with more liberal faculties.

Similarly, the political scientists M. Kent Jennings and Laura Stoker analyzed data from a survey that tracked the political attitudes of about 1,000 high school students through their college years and into middle age. Their research found that the tendency of college graduates to be more liberal reflects to a large extent the fact that more liberal students are more likely to go to college in the first place.

Studies also show that attending college does not make you less religious. The sociologists Jeremy Uecker, Mark Regnerus and Margaret Vaaler examined data from the National Longitudinal Study of Adolescent Health and found that Americans who pursued bachelor’s degrees were more likely to retain their faith than those who did not, perhaps because life at the bottom of the socioeconomic ladder can be rough in ways that chip away at religious belief and participation. They report that students “who did not attend college and two-year college students are much more likely — 61 and 54 percent more, respectively — than four-year college students to relinquish their religious affiliations.”

So why do conservatives persist in attacking higher education? There’s no doubt that in terms of overall curricular content and campus culture, most colleges and universities do skew more to the left than to the right. And research by the sociologists Amy Binder and Kate Wood confirms that this can be a frustrating and alienating experience for conservative students, even if it’s not serving to indoctrinate anyone.

But that alone doesn’t explain the intensity of the animus. Doing so requires some historical perspective. Conservatives have been criticizing academia for many decades. Yet only once the McCarthy era passed did this criticism begin to be cast primarily in anti-elitist tones: charges of Communist subversion gave way to charges of liberal elitism in the writings of William F. Buckley Jr. and others. The idea that professors are snobs looking down their noses at ordinary Americans, trying to push the country in directions it does not wish to go, soon became an established conservative trope, taking its place alongside criticism of the liberal press and the liberal judiciary.