What Happens To The Iran Deal Once Congress Gets Back From Recess?

U.S. Senator Jeff Merkley, a Democrat from Oregon, said on Sunday he would support the nuclear deal with Iran, moving President Barack Obama a step closer to having sufficient backing to ensure the deal stands.

"I believe the agreement, titled the Joint Comprehensive Plan of Action (JCPOA), is the best available strategy to block Iran from acquiring a nuclear weapon," Merkley wrote in a statement published on Medium.com.

Obama is trying to muster 34 votes in the Senate to ensure lawmakers cannot kill the deal. Thirty-one senators, all Democrats and independents who vote with Democrats, have now said they will support it.

Congress must vote on the deal by Sept. 17. The following describes how votes are likely to play out: