Imagine you are one of House Speaker Nancy Pelosi’s top political strategists. The polls show your party needs a game-changer, something that will transform what looks like a losing political hand into a winner. “I know,” you shout, “let’s push for a large tax increase on the ‘fortunate few’ — the 2 or 3 percent of the population with so much money they won’t even miss a few thousand bucks. The other 97 or 98 percent will feel no pain, and we’ll be able to call ourselves deficit hawks when all those billions start rolling in.” On paper, this strategy...