As Congress returns from recess and prepares for important votes on President Obama’s nuclear deal with Iran, many in Washington are already declaring the debate over. But the looming showdown over a resolution to disapprove the deal is no mere show vote.

It’s true that through the raw exercise of power, Obama appears to have found a way to get his Iran deal around Congress despite bipartisan disapproval and opposition of the public. Even in the face of a presidential veto, however, there are still national security reasons for Congress to vote to reject the dangerous deal.