One of the left’s more charming conceits is the certitude that it has bonded with the common man, that it has a picture window on his soul. The left still thinks it can lead a popular uprising – that the people are out there, just waiting for a down-with-capitalism, single-payer-health-care, we-could-be-as-great-as-North Korea message – hungry to be led to the collectivist Big Rock Candy Mountain by activists who’ve never come closer to blue-collar types than reading the ruminations of Karl Marx – a man who never once set foot on a factory floor. “Progressives Say American Dream Movement Rivals Tea...