Reptilian. Shameless. Greedy. Nauseating. Criminal.

These are the types of adjectives that every so often—the interval between episodes never lasts long—are inspired by one story or another about this or that member of Congress.

As it happens, we are in one of those seasons again. Perhaps you long ago relinquished your faith that most lawmakers are decent, conscientious, responsible people who are concerned first and above all with legislating in the public interest, and only then turn their attentions to their own earthly appetites.

Even so, some of these recent cases are out there: allegations of underage sex trafficking, unwanted public groping, resume-padding, and other manifestations of human weakness and depravity.

One useful thing about extreme behavior, however, is that it can help illuminate prevailing norms—the non-extreme, perfectly ordinary reality. So at a time when a lot of recent coverage of lawmakers revolves around allegations, or documented evidence, of unacceptable behavior, it seemed in a peculiar way an apt moment to look at Congress through the prism of a different noun: Mediocrity.

As an informal poll, I recently asked a bunch of people […]