The polls are all over the place on the "Iran Nuclear Deal", with one of the latest showing the public opposed to the deal by nearly two to one. See the WP story here.
My analysis is that if the deal is good, then it would sell itself--the president could be a poor leader and the deal would be popular. A good product sells itself. If the deal was bad and we had a very persuasive president, he could move opinion. There are many elements to this ability beyond persuasion alone. If the public had seen the president take stands which were unpopular in the past and they worked out well, this would build credibility. Also, presidents who own their mistakes gain credibility as well. As has been pointed out here in the past, Obama takes credit for anything that works out well, even if he opposed the plan. He also blames others when things that he promoted go badly. He has no credibility with the broad public.
Since the deal is not popular, we can only conclude that it is a bad deal. And Obama is a bad leader.