This is not a new scenario. Congress is unlikely to be able to sustain a veto. If they do, the President is prepared to do it on his own authority.
It started with not bringing it as a treaty in the first place. It continued by taking it to the United Nations first.
It seems unlikely that Congress will deep-six Obama’s nuclear deal with Iran. But just in case, the administration floated a trial balloon in Politico this week, detailing how he could work around congressional opposition to help Islamic Republic:
Obama has broad powers to act alone — even against the will of Congress — say experts and former administration officials familiar with internal deliberations. Using his executive branch authority, Obama could effectively halt many U.S. sanctions on Iran, they say, in a bid to persuade Tehran to meet its end of the bargain.
Obama has almost exclusively functioned “against the will of Congress.” It’s somewhat ironic that the eponymous “Obamacare” is essentially the sole achievement of this presidency secured with the help of legislators. Nothing, neither immigration nor climate change policy nor housing policy nor this Iranian deal, will have been crafted or approved by the legislative representatives of the American people with the proper checks and balances they deserve. And the framework for passage of the Iran deal, thanks to Republicans like Bob Corker, features a threshold higher than the filibuster which Democrats were constantly griping about when they held the majority.