US unions plan attack on Donald Trump in attempt to derail presidential bid Concerned labor group leaders are organizing ad campaigns and phone banks as Trump’s populist message on trade and jobs draws in union voters The prospect of a Donald Trump nomination has labor leaders scrambling to hold the line as the Republican frontrunner’s appeal to disaffected working-class voters threatens to upset the traditional political calculus. The majority of America’s almost 15 million unionized workers can be usually be relied upon to back the Democratic candidate in a presidential year, but leaders are concerned by Trump’s populist message on...