The deal just struck between the U.S., world powers, and Iran is an historic achievement that decreases the likelihood of an Iranian nuclear weapon and forestalls the risk of another costly U.S. war in the Middle East.

But while the diplomats in Vienna are finished wrangling over the final details, the Obama administration is by no means finished fighting for the agreement’s survival. Congress has 60 days with which to review the deal for final approval, and while Republicans may not have a veto-proof majority, they — along with some Democrats — remain vehemently opposed to any plausible peaceful resolution.

The debate over Iran diplomacy was really two debates, in which each side was arguing over something different. On the one side was a strikingly broad consensus of nearly the entire arms control community, which recognizes what the deal can achieve in terms of nonproliferation and regional stability. On the opposing side is the Iran hawk community, which focused less on the nuclear issue than on finding ways to isolate and ultimately destroy Iran’s clerical regime, by military force if necessary, nuclear program or not.

The near-consensus among arms controllers is due to the deal’s strong nonproliferation features. Under the deal, Iran would reduce its stockpile of centrifuges by two-thirds and dismantle about 97% of its low-enriched uranium. For 15 years, the Iranians will be prohibited from enriching any uranium at their Fordow site and the Arak reactor for plutonium production would be permanently disabled.

Throughout, Iran would be subject to one of the most robust and intrusive inspection regimes in the world, with continuous video monitoring of its uranium mines for the next 25 years and monitoring of centrifuge production facilities for 20 years. Expanded inspections under the Additional Protocol are permanent.

As 30 nonproliferation experts attested to in a statement in April, “the agreement reduces the likelihood of destabilizing nuclear weapons competition in the Middle East, and strengthens global efforts to prevent proliferation, including the Nuclear Nonproliferation Treaty.”

Under the deal, Iran’s breakout time — the amount of time it would take to produce one bombs-worth of highly enriched uranium if it decided to do so — would be extended to roughly one year, up from roughly three months at the interim agreement’s inception.

To review these technical parameters and feverishly warn that the deal “paves the way for a nuclear Iran,” as Sen. David Perdue, R‑Georgia, and others recently have is bizarre. Similarly, to declare as Sen. Marco Rubio, R‑Florida, recently did that the deal would produce “a cascade of proliferation” in the region relies on an array of interlocking dubious assumptions.

What these wildly divergent assessments seem to indicate is that the sides were arguing over different problems. For the arms control community, the problem was an Iranian nuclear weapons capability. For them, given the one-two punch of political reality and the terms of the agreement, the deal was a good thing. It significantly reduced the probability of an Iranian nuclear weapon and could meet both sides’ minimum standard of necessity.

For neoconservatives and interventionist Democrats, the nuclear program was but one piece of a much larger problem: a looming Persian menace that threatened to dominate the Middle East. This explains the specious nonproliferation arguments offered in opposition to the deal, as well as the increased warnings of Iranian “regional hegemony” heard in the run-up to the deal.

These sorts of arguments are tendentious in the extreme, because on their own terms they fall short. The nuclear agreement is indeed helpful from the point of view of nonproliferation, and Iran has no path to regional hegemony in the policy-relevant future. Instead, these claims seem to be part of a larger strategy under which everything that happens tied to Iran is treated as a threat.

But the question in the context of nuclear diplomacy was never a choice between a neutered, Israel-recognizing liberal Iran or an empowered nuclear theocracy. It was between a nasty but weak regional power with little power-projection capability, closer or further away from a nuclear weapons capability. And on these terms, the agreement must be viewed as a clear success.