The rhetoric I hear from the right is all about "Obama's deal with Iran", with the suggestion that it will fall apart if is not approved by Congress, or is reneged on by a future president.
I'm puzzled by this assurance on the part of the right. The US is just one of the countries that has been imposing sanctions on Iran, and the agreement between Iran and the US, China, Russia, France, Britain, and Germany means that sanctions will be lifted, and trade will resume. So what if the US reneges? The other five major countries will be ending the sanctions as long as Iran keeps to its end of the bargain, allowing continuing inspections of its nuclear sites by the IAEA. So businesses in those countries can expect to profit from the renewed trade, but US businesses won't if the US alone insists on keeping up the sanctions.
And once the other countries have resumed normal relations with Iran, leaving the US isolated, what do the renegers propose? The two options I hear are "Go back for a better deal" (as though the deal was solely a US deal, and was not hammered out through years of negotiations with all parties as the best deal that could be made), or military action. Can anyone seriously propose unilateral military action once the rest of the international community has accepted the Iran deal? Well - I suppose the crackpots of the right might continue their warmongering rhetoric, but to put it into practice against the wishes of every other major power? Could they really be that crazy?
Update 8/14/2015 Fareed Zakariah takes Senator Schumer to task for opposing the deal:
Rejecting this deal would produce an Iran that ramps up its nuclear program, without inspections or constraints, with sanctions unraveling and a United States that is humiliated and isolated in the world.