Durbin, the No. 2 Senate Democrat, is leading the effort to round up Senate support for the international deal that aims to curb Iran's nuclear program in exchange for billions of dollars in relief from economic sanctions. [...] to the surprise of many, supporters of the Iran deal are piling up enough votes that they may even be able to block a resolution of disapproval in the Senate next month, meaning President Barack Obama wouldn't have to use his veto pen — an outcome that looked all but inconceivable in the days after the deal was signed July 14. Schumer and Murray declined interview requests, and Schumer's aides have repeatedly denied that Schumer is whipping senators against the Iran deal, saying that the phone calls he's made have been to apprise others of his stance against the agreement, not twist their arms. [...] opposition from Schumer, the most influential Jewish lawmaker, was seen as having the potential to move other Democrats against the deal, which faces vehement opposition from Republicans and from Israeli leaders who fear it will only empower an enemy sworn to their destruction. [...] too, he's gotten crosswise with some of his most reliable constituents, black supporters who would like to see a black Democrat in the seat once held by Obama and question Durbin's early endorsement of Duckworth, a double-amputee Iraq War veteran.