The senior senator from New York is set to become the chamber’s most powerful Democrat, after Harry Reid of Nevada retires later this year. Both Reid and Democratic whip Dick Durbin have endorsed Schumer to become the next minority leader – or majority leader, if Democrats succeed in retaking the Senate come November.Schumer would be the first-ever Jewish figure to occupy the post. But this particular candidate has bucked the leader of his own party, US President Barack Obama, on several significant initiatives, most notably on the Iran nuclear deal, which Schumer staunchly opposed.“I wouldn’t be surprised” if Democrats in the caucus hold his Iran vote against him, a passive-aggressive White House Press Secretary Josh Earnest said at the time. “There’s no denying that this difference of opinion that emerged overnight is one that has existed between Senator Schumer and President Obama for over a decade.”Should Clinton win the presidency, Schumer will serve as a critical ally of a former colleague: the two figures served New York in the Senate during the trying period following the September 11 attacks.But its a two-way street for Schumer, as a President Clinton will also serve as a critical ally for him. Breaking from Obama last spring, she came out in support of a bill written by Schumer titled the Justice Against Sponsors of Terrorism Act. It would allow the families of September 11 victims to sue foreign sponsors of terrorism in federal courts.Schumer has served New York in the Senate since 1999.