Matt Bai's article in Democracy has drawn a bit of attention today, particularly this paragraph:

Generally speaking, political writers don't think so much of political scientists, either, mostly because anyone who has ever actually worked in or covered politics can tell you that, whatever else it may be, a science isn't one of them. Politics is, after all, the business of humans attempting to triumph over their own disorder, insecurity, competitiveness, arrogance, and infidelity; make all the equations you want, but a lot of politics is simply tactile and visual, rather than empirical. My dinnertime conversation with three Iowans may not add up to a reliable portrait of the national consensus, but it's often more illuminating than the dissertations of academics whose idea of seeing America is a trip to the local Bed, Bath & Beyond.

This is odd, to say the least. Bai is essentially arguing on behalf of the very approach he mocks.

In terms of a reporter's ability to paint a “portrait of the national consensus,” a dinnertime conversation with three Iowans is pretty much the same thing as thinking you can see America via a trip to the local Bed, Bath & Beyond.

The problem with extrapolating what you see on a trip to Bed, Bath & Beyond into an assertion about broader public opinion is that it mistakes anecdote for data. A dinnertime conversation with three Iowans has the same problem. And Matt Bai knows this; just a few paragraphs earlier, he wrote:

Academics who study politics often consider those of us who write about the field to be superficial, simple-minded and-the greatest indictment of all- unscientific . We interview three people in an Iowa diner and act as if we have penetrated the very soul of America. (Such allegations are, sadly, true enough.)

More Bai:

The founder of Daily Kos, Markos Moulitsas Zuniga, is a law school graduate who lives in Berkeley; the lead blogger on FireDogLake, Jane Hamsher, used to be the Hollywood producer of such family films as “Natural Born Killers”; Chris Bowers, the signature voice of Open Left, is (or at least was when I first met him) a graduate student in sociology. To suggest that the voices of 100 or so prominent bloggers of similar pedigree represent some new, more inclusive voice of the American everyman-which is what the bloggers themselves like to profess-is just fantasy.

Well, ok. But Bai just gone done arguing that his dinnertime conversations with three Iowans are illuminating. The views of “three Iowans” are illuminating, but those of three bloggers are not? (By the way, note the loaded descriptions of those three: Bai could just as easily have described Markos as a veteran of the U.S. Army or as a small business owner who grew up in El Salvador. But that would have undermined his point pretty badly.)

So Matt Bai seems to be arguing that looking at a narrow and small slice of the populace in order to draw broader conclusions is invalid - unless Matt Bai is the person doing the looking.