To hear Donald Trump tell it, blue-collar workers here are suffering as much as ever, their livelihoods endangered by the familiar combination of foreign competition and U.S. companies eager to hold down labor costs. It's Trump's mantra. He repeats it again and again at campaign stops like the one he made here last week. A leading contender for the Republican presidential nomination, Trump has made the health of the U.S. manufacturing a cornerstone of his insurgent campaign. In doing so, Trump is targeting a big pool of potential voters among disaffected blue-collar workers, even if it means alienating the business...