One thing leads to another. Complain bitterly that the Senate filibuster undermines democracy and you wind up concluding that the Senate’s existence is undemocratic. In 2009 the Washington Post’s Ezra Klein, for example, punctuated a long series of blog posts criticizing the filibuster with one allowing that while the Senate is “very important,” it is also “resolutely, aggressively, anti-democratic.”

The crucial defect, according to Klein and others, is that equal representation of states guarantees unequal representation of people. The 38 million Americans who live in the 22 least populous states send 44 senators to Washington, while the 37 million living in …