The historian KC Johnson has an interesting, link-filled article on ideological and intellectual diversity at Inside Higher Ed:

Inside Higher Ed recently reported on four University of Pittsburgh professors critiquing the latest survey suggesting ideological one-sidedness in the academy. According to the Pitt quartet, self-selection accounts for findings that the faculty of elite disproportionately tilts to the Left. "Many conservatives," the Pitt professors mused, "may deliberately choose not to seek employment at top-tier research universities because they object, on philosophical grounds, to one of the fundamental tenets undergirding such institutions: the scientific method."

Imagine the appropriate outrage that would have occurred had the above critique referred to feminists, minorities, or Socialists. Yet the Pitt quartet's line of reasoning — that faculty ideological imbalance reflects the academy functioning as it should — has appeared with regularity, and has been, unintentionally, most revealing. Indeed, the very defense offered by the academic Establishment, rather than the statistical surveys themselves, has gone a long way toward proving the case of critics who say that the academy lacks sufficient intellectual diversity.

Johnson then critiques three excuses for ideological homogeneity:

1. The cultural left is, simply, more intelligent than anyone else. As SUNY-Albany's Ron McClamrock reasoned, "Lefties are overrepresented in academia because on average, we're just f-ing smarter." The first recent survey came in early 2004, when the Duke Conservative Union disclosed that Duke's humanities departments contained 142 registered Democrats and 8 registered Republicans. Philosophy Department chairman Robert Brandon considered the results unsurprising: "If, as John Stuart Mill said, stupid people are generally conservative, then there are lots of conservatives we will never hire." . . .

2. A left-leaning tilt in the faculty is a pedagogical necessity, because professors must expose gender, racial, and class bias while promoting peace, "diversity" and "cultural competence." According to Montclair State's Grover Furr, "colleges and universities do not need a single additional 'conservative' .... What they do need, and would much benefit from, is more Marxists, radicals, leftists — all terms conventionally applied to those who fight against exploitation, racism, sexism, and capitalism. We can never have too many of these, just as we can never have too few 'conservatives.'" . . .

3. A left-leaning professoriate is a structural necessity, because the liberal arts faculty must balance business school faculty and/or the general conservative political culture.

In an earlier post, I mentioned John McGinnis's forthcoming Georgetown Law Journal study of political diversity on law faculties. Adam Liptak has a fair account of it in the New York Times:

The study, to be published this fall in The Georgetown Law Journal, analyzes 11 years of records reflecting federal campaign contributions by professors at the top 21 law schools as ranked by U.S. News & World Report. Almost a third of these law professors contribute to campaigns, but of them, the study finds, 81 percent who contributed $200 or more gave wholly or mostly to Democrats; 15 percent gave wholly or mostly to Republicans.

The percentages of professors contributing to Democrats were even more lopsided at some of the most prestigious schools: 91 percent at Harvard, 92 at Yale, 94 at Stanford. At the University of Virginia, on the other hand, contributions were about evenly divided between the parties. The sample sizes at some schools may be too small to allow for comparisons, though it bears noting that by this measure the University of Chicago is slightly more liberal than Berkeley. . . .

Whatever may be said about particular schools and students, professors and deans of all political persuasions agreed that the study's general findings are undeniable.

"Academics tend to be more to the left side of the continuum," said David E. Van Zandt, dean of Northwestern's law school, where the contribution rate to Democrats was 71 percent. "It's a little worse in law school. In other disciplines, there are more objective standards for quality of work. Law schools are sort of organized in a club structure, where current members of the club pick future members of the club."

Although not mentioned in the NY Times report, McGinnis's article also examines those letters by groups of "experts," eg, the public letters favoring or opposing Clinton's impeachment or opposing Bush v. Gore. Despite hundreds of signatories to the various letters, McGinnis said only three professors (and I'm one of the three) has donated exclusively to candidates at odds with the implied political orientation of the signed letter.

UPDATE [further Updated]: The Times article raises the question whether it matters if there is political diversity on law faculties.

I have two answers--one substantive, one speculative. First, in my studies with the General Social Survey, political ideology is the strongest predictor of views across a range of hundreds of issues that I've looked at--stronger than race, gender, education, class, occupation, age, region, marital status, etc. Those who say that labels such as "conservative" and "liberal" are meaningless today are frankly uninformed. Most survey researchers know that these labels are quite salient.

Second, a professor at the Harvard Law School told me that in 1988 he asked every member of the Harvard Law School faculty with even a hint of conservative or Republican leanings whether they favored or had voted for Bush in 1988. Only one had (1 out of 60-80 faculty); all others favored Dukakis. He also said that in about 2 or 3 dozen entry-level faculty hires from the mid-1970s through about 3 or 4 years ago (when they hired an entry-level conservative), the Harvard Law School had not hired a single Republican.

Now consider this thought experiment: [Imagine that in 1988 all but one of the Harvard Law faculty had favored Bush1 over Dukakis. And] Imagine that over the same period of a quarter century [mid 1970s through early 2000s], the Harvard Law School had hired at the entry-level only those who leaned Republican. Imagine how different the Harvard Law School would be, how different legal education would be, how different the government (and public policy) would be, populated with lawyers trained by an overwhelmingly Republican Harvard faculty. Somehow I think it would be a different world.

ANOTHER UPDATE: Professor Bainbridge weighs in thoughtfully on the topic.

So does sociologist Chris Uggen.