Democratic Sen. Tom Carper on Friday became the 30th senator to announce support for the Iran nuclear deal, as momentum for the White House-backed agreement grows. If Senate Democrats can amass 41 votes in favor of the deal, they could block passage of a congressional resolution to disapprove of the deal. If that doesn’t happen and the Republican-led Senate votes to disapprove of the deal, President Barack Obama has vowed to veto it. Democrats then would need 34 votes — four more than they have now — to prevent a congressional override of the presidential veto. A vote on the nuclear deal the U.S. and other world powers negotiated with Iran is scheduled for early September.