On Tuesday morning, an additional three Senators publicly voiced their support for the nuclear agreement, bringing the number of supporters to 41.
As a procedural rule, Senate opponents of the Iran deal will need 60 members in order to bring a resolution of disapproval to the floor for a final vote.

The 41 supporters of the deal now have the ability to block that vote, or filibuster. If the Iran deal supporters were to filibuster, they could run out the clock to the September 17 deadline, granting congressional approval for the nuclear agreement by default.