As reported by the Washington Post, U.S. Senator Barbara Mikulski (D-MD) has announced her support for the Iran Nuclear Deal. As the 34th U.S. Senator to do so, this secures enough support to protect President Obama's promised veto, if and when expected congressional measures of disapproval are passed, by majority vote, in the U.S. Senate and House before Sept. 17, the deadline for such an action. President Obama needs only one house of Congress to sustain his veto, in order to stave off congressional disapproval and secure the Iran Nuclear Deal negotiated by his Secretary of State, John Kerry.
There is some possibility still remaining that President Obama won't need to use his veto pen. If 41 U.S. Senators support the Iran Nuclear Deal, they can successfully filibuster a vote on disapproval -- meaning the pact can be secured that way, as well.