From Bernie Sanders’s attacks on the rich to Donald Trump’s pledge to help the U.S. “win” in its trade with China, economic issues have been central to the presidential race in both parties this year. Today’s Super Tuesday contests in 12 states will give the clearest picture yet of how the candidates’ economic messages are connecting with voters.The first two states to vote this year, Iowa and New Hampshire, both have fairly strong economies that don’t much resemble the broader national situation.