The debate over the Iran deal is, in many ways, about complex, technical issues of nuclear development and verification. But it really boils down to one core question: whether you think negotiating a deal with Iran is the best way to solve the Iran nuclear issue.
These two tweets sum up the simplest pro- and anti-deal arguments pretty succinctly.
The simplest case for the deal is the idea that the only alternative to solving Iran's nuclear program is war, and that war is undesirable. The pro-deal thinking is that a deal heads off war, and increases our ability to stop Iran from getting a nuclear weapon. The Intercept's Maz Hussain put the basic impulse behind the argument really well:
Sorry to everyone who was looking forward to another big war.— Murtaza Hussain (@MazMHussain) July 14, 2015
The anti-deal thinking, by contrast, is that any viable nuclear deal actually makes things worse. Deal critics see the Iranian government as implacably hostile to the United States and hell-bent on getting nuclear weapons: They'll pocket sanctions relief, cheat on the deal, and simply acquire a bomb when its terms expire. For people like the Weekly Standard's Stephen Hayes, then, the deal isn't a way of hedging against an Iranian bomb; it's a way of guaranteeing it:
The #IranDeal finalizes US shift from preventing an Iranian nuclear weapons to managing the process by which Iran goes nuclear.— Stephen Hayes (@stephenfhayes) July 14, 2015
On this view, it's better to scrap the deal, keep up sanctions, threaten war, and eventually try to force Iran into total capitulation — even if we have to go to war to do it.
So that's the debate. Deal supporters think the deal, as is, is the only realistic alternative to war or a nuclear-capable Iran; opponents think the deal makes a nuclear Iran more likely and that war is a preferable alternative. This is a debate about the big pictures, not the details.