What if Congress rejects the Iran deal? Ex-Mossad chief Halevy fills in the blanks

There's one incontrovertible point in the argument against the Congress rejecting and invalidating the nuclear agreement with Iran. Even if you think the deal was poorly negotiated, if the U.S. walks away the sanctions regime will immediately fall apart and Iran will gain everything it could ever gain either by cheating on the deal or stepping up its enrichment and weapons program when various constraints expire. 

Obama has made this point repeatedly, minus the "even if you think..." part. The shorthand is "what is your alternative?" -- and there is none. Implicitly recognizing this, Chuck Schumer, in the most self-negating policy statement I've ever read, could barely bring himself to sketch in (in the statement's last breath) an alleged alternative path:

Better to keep U.S. sanctions in place, strengthen them, enforce secondary sanctions on other nations, and pursue the hard-trodden path of diplomacy once more, difficult as it may be.

Unlike many, Schumer acknowledges here that post-deal U.S. sanctions would be unilateral -- not only unilateral, but punitive against friend as well as foe. As for the "path of diplomacy," he doesn't map it because he can't -- the U.S. would have no partners and no leverage.

Obama has been somewhat abstract in making the case that the U.S. would stand alone if the Congress scotches the deal and thus jilts the country's negotiating partners. Efraim Halevy, a former head of the Israel's Mossad, has filled in the blanks. The administration might borrow some talking points here:

If the US neglects the agreement, it will fall apart.

 This means Iran will be free to renew its nuclear activities - the facility in Arak, for example, which under the agreement is supposed to be completely dismantled, could resume plutonium production, which is an alternative path to a nuclear bomb, in addition to uranium enrichment.

Furthermore, the international sanctions regime will collapse. The US will be the only country to maintain its sanctions, while Russia and China will rush to renew arms sales to Tehran, with Moscow helping the Islamic Republic develop its missile arsenal, as it has done in the past.

Schumer, like most deal opponents, complains that sanctions relief will free up cash that Iran can use to fund its proxies. Set that against the combination of worldwide except-the-US sanctions relief and full access to the international weapons bazaar. It's kind of like taking away your child's allowance to keep him from dealing drugs.

In structuring a "resolution of disapproval" option that Obama would sign, Congress gave him the equivalent of fast-track status. When the deal was agreed upon, the world changed. Rejection is not an option, even if you don't like the deal.