Under the headline "Obama was right, Iran capitulated," Efraim Halevy enumerated several reasons.
Among them: Iran would be forced to submit to unprecedented supervision, its supply of centrifuges and low-enriched uranium stockpiles would be drastically reduced, it would be unable to manufacture fissile material for 15 years, etc.
"Anyone who has followed events in Iran in recent decades or has studied the matter has to admit truthfully that he never believed Iran would ever agree to discuss these issues, let alone agree to each of the clauses I have mentioned," Halevy concluded.
Here in America, though, the man who has emerged as the foremost critic of the deal dismisses such optimism.
"There is no nuclear deal or framework with Iran," declares the website of Senator Tom Cotton, who leads an informal group of congressional Republicans.
"There is only a list of dangerous U.S. concessions that will put Iran on the path to nuclear weapons."- Israeli military option still possible, despite nuclear deal
It was Cotton who originated the letter to the Iranian leadership during the negotiations, signed by 46 Republican colleagues, warning that the next president (he seemed to presume it would be a Republican) could cancel any agreement negotiated by Obama with "the stroke of a pen."
So. Who are you going to believe?
Tom Cotton is a 38-year-old junior U.S. senator from Arkansas, who sits on a couple of congressional subcommittees.
Efraim Halevy is the former head of Mossad, the Israeli foreign intelligence agency.
Ferreting out the ingenues
Now, it is true that Halevy has been retired for nearly 14 years.
But then, the man who succeeded him as Israel's chief spy, Meir Dagan, seems to share Halevy's view of Israeli Prime Minister Benjamin Netanyahu and his campaign, coordinated with congressional Republicans, to sink the deal.
Last month, as Netanyahu stood in the well of Congress denouncing Obama's negotiations with Iran, Dagan, who ran the Mossad until four years ago, actually serving under Netanyahu, muttered "bullshit" live on Israeli TV.
In an interview later, Dagan said Netanyahu lied both about the reach of Iran's missiles and how close its scientists are to producing a bomb.
But maybe, in the view of American Republicans and their super-rich backers, both Halevy and Dagan are naïve ingenues with no real understanding of Israeli or American security needs.
So let's examine the recent words of Yuval Diskin, the former chief of Israel's internal security service, the Shin Bet:
"From first-hand knowledge I can say that Dagan has done more about the Iranian nuclear threat and other security-related issues than Netanyahu and all the other Likud spokespersons combined," Diskin wrote recently on the website of Israel's i24 News.
"Unlike Netanyahu, what he did was not just to speak at the UN or in Congress — and I am not belittling the importance of either. When the day comes, the people of Israel will know and understand what I'm talking about."
Move out the furniture
It's not terribly hard to imagine what Diskin is referring to, given the remarkable setbacks Iran's nuclear scientists have been dealt by outside forces in recent years.
Enough with the Israeli experts, though. What about the people here in America who have spent entire careers studying such matters?
I emailed Halevy's article to Joseph Cirincione at Project Ploughshares, one of the foremost disarmament experts in the world.
"It will not surprise you that I agree," he wrote back. "This deal is a victory for both sides. Iran gets to keep its buildings. And we get to move out most of the furniture. Brilliant."
Killing the deal, says Cirincione, would be "idiotic."
If the Republican-dominated Congress takes steps to do that, or to impose further sanctions, he said, "the sanctions regime will unravel.
"We will be seen as the reason the deal failed. Global support for sanctions will wither. The pressures on Iran will get weaker, not stronger."
Cirincione is not the only U.S. expert saying such things.
In Mother Jones magazine, David Corn recently published a roundup of opinions from eight of the country's most distinguished authorities on nonproliferation: people like Anthony Cordesman, a former intelligence chieftain at the Pentagon; William Burns, a former deputy secretary of state; and assorted experts from Harvard and Princeton universities.
All effectively concurred the deal is the best chance available to contain Iran's nuclear ambitions.
Further, polls suggest most Americans, while dubious of Iran's good faith, nonetheless support the deal.
So why such determination within the Republican Party to kill it before it even takes effect?
Follow the money?
Well, GOP politicians appear to believe that Iran will, one way or the other, achieve a bomb unless they are punished into utter submission.
They point out that Iran is ruled by unelected theocrats (overlooking, of course, that the last freely elected Iranian leader, Mohammed Mosaddegh, was covertly overthrown by the CIA, on behalf of American oil interests, decades ago).
The Republicans also believe, as many Americans do, that Obama's foreign policy record has been weak (although nothing like that of his predecessor, who invaded Iraq on a pretext, and put American troops on Iran's eastern and western borders).
And money might have something to do with it, too.
Hawkish pro-Netanyahu U.S. billionaires are making some hefty contributions to Senator Cotton and his anti-deal cohort.
A group called the "Emergency Committee for Israel" bankrolled Cotton's election campaign last year to the tune of nearly $1 million. The New York Times recently had a hard look at the money behind the scenes.
Of course it's possible the Republicans truly believe they and their backers really do know more about the Iranian threat than people like Ephraim Levy, Meir Dagan and Yuval Diskin, not to mention most of America's important allies.
Or perhaps it's just the usual wound-the-president politics, coordinated this time by the junior senator from Arkansas.
But if they do manage to gut or kill the deal, Cirincione told me, "We will be left with one of two choices: watch Iran vastly expand its nuclear program or go to war."
It's possible there are some Republican hawks who would actually prefer the latter option. It wouldn't be the first time.