The immune system of the modern body politic is nothing if not resilient, and this summer all of its antibodies seem to be trained on heretofore little known Congressman Paul Ryan. That makes this a particularly instructive moment, because the attacks on the Wisconsin Republican show how deeply his radical honesty is subverting Washington's flim-flam—to borrow a phrase.

"The flim-flam man" is what Paul Krugman called Mr. Ryan in a New York Times column last week that set a spleen-to-substance record...