Opposing Iran Nuclear Deal, Chuck Schumer Rattles Democratic Firewall

WASHINGTON — The decision by Senator Chuck Schumer of New York to oppose the Iran nuclear deal has rattled the Democratic bulwark around the accord, emboldened the deal’s opponents in both parties, and set off a wave of condemnation from liberals for the man who hopes to lead Senate Democrats in the next Congress.

But supporters of the accord said on Friday that Democratic defections would not be enough to bring it down.