What does "middle class" mean?

Dionne Searcey and Robert Gebeloff do a nice job crunching some numbers on what sorts of people are part of the middle class, and how they’re doing (the short version: not great). This caveat of theirs, however, is an important one:

The definition here starts at $35,000 — which is about 50 percent higher than the official poverty level for a family of four — and ends at the six-figure mark. Although many Americans in households making more than $100,000 consider themselves middle class, particularly those living in expensive regions like the Northeast and Pacific Coast, they have substantially more money than most people.

Indeed—yet politicians have for the most part persisted in including the mildly rich, earning up to a quarter million a year, under the “middle class” umbrella. And they can do this, because like “natural food” or “war as a last resort,” it’s not a term that has any officially regulated meaning. So Searcey and Gebeloff have to begin their calculations by defining “middle class” for their purposes. Theirs is a pretty good definition, but it’s not a consensus one or one that necessarily carries tons of weight among policymakers.