Just as Rick Santorum has pointedly and repeatedly reminded voters that Mitt Romney supported an individual health care mandate and the Wall Street bailouts, so Mitt Romney has sought to remind voters that Rick Santorum has been cozy with Big Labor in the past. In his attacks on Santorum, Romney has sounded unequivocally anti-labor, which no doubt has not helped him much in Michigan. Today, though, the former Massachusetts governor displayed a nuanced perspective on labor unions, characterizing himself as pro-union-worker but anti-union-bosses. His first line — “Labor unions play an important role in our society” — might seem to...