The administration has felt pressure to move quickly on talks with Iran because of the pace at which Iran is building its nuclear capacity; if there is no progress in the next several months, it plans to seek Security Council support for tougher sanctions.The ongoing power struggle in Tehran doesn’t synch with that timetable. But it also seems to offer a considerably better chance for positive change than either negotiations or a sanctions strategy (which very likely would be undermined by Russia). While the administration should remain open to constructive proposals by Iran, it should avoid any action that would lend strength to Mr. Khamenei’s regime. And Mr. Obama should continue to make clear that the United States stands with those seeking peaceful and democratic reform.