WASHINGTON, D.C. — President Barack Obama suffered a notable setback in his all-out campaign to secure Democratic support for the Iran nuclear deal when the leading Jewish Democrat in the Senate announced his opposition. The question is how significant the blow will turn out to be. Republicans, infuriated by Obama's recent comparison of GOP foes of the pact to "Death to America" Iranian hardliners, immediately focused on the stunning break with the president by Chuck Schumer of New York, and they're urging other Democrats to buck the administration. But there was no quick indication that the announcement by Schumer, the No.