This post was updated at 11:35 a.m. ET
Congress is back with a daunting must-do list. But its first order of business will be the Iran nuclear deal, as a deadline looms on Sept. 17. Even though the deal is basically done, as NPR's Ailsa Chang reports, Congress could still spend days hotly debating it.
It's an unusual vote (as NPR's Steve Inskeep explained) — instead of voting on whether to approve the Iran deal, Congress would vote on whether to disapprove it. The president now has 41 senators supporting his deal, which means it looks certain to survive the opposition of Republicans in Congress. (It is not clear that all 41 would vote to prevent the bill from coming to the floor, though.)
Here's a look at how the Iran vote would work and why it's not quite business as usual on Capitol Hill: