Barack Obama said during his 2012 presidential campaign that "as long as I'm president of the United States, Iran will not get a nuclear weapon."

There's been a lot of debate about how effective Obama's approach has been in halting Iran's program to develop a nuclear weapon. But this promise is narrower. The key question for judging this promise is whether, as Obama nears the end of his tenure in the White House, Iran currently has one or more nuclear weapons. And that question is far less controversial -- the overwhelming evidence is that as of today, Iran is not a nuclear-armed state.

The big development since our previous update to this promise was the nuclear deal struck between the United States, key allies and Iran in July 2015. At root, the agreement lifts international economic sanctions on Iran in exchange for it agreeing to curb nuclear technologies and allow inspections for 10 to 25 years.

Specialists say the best evidence indicates that Iran does not presently have a usable nuclear weapon.

"I think a reasonable analysis would show that they do not," said Richard Nephew, a Columbia University foreign-policy specialist who earlier served as Obama's Iran director at the National Security Council.

Ted Bromund, a foreign policy specialist at the conservative Heritage Foundation who is not a fan of the Iran deal, concurred.

"You can test a bomb on a computer if you know what you are doing, but most nuclear programs -- such as India, Pakistan, and China, and indeed the U.S. and the former Soviet Union -- want to test in real life initially," Bromund said. "So if Iran does not test a bomb by Jan. 20, 2017" -- the day Donald Trump is inaugurated -- "the odds are good that they do not have one."

For Nephew, a key piece of evidence is nuclear material. "There has been no report of a significant quantity of weapons-usable material being diverted in the country, and this is going back many, many years," he said. In addition, evidence gathered from nuclear negotiations with Iran produced "no indications that Iran has undeclared facilities capable of producing such material or fashioning a nuclear weapon."

We should note that it would be a bridge too far to say that Obama deserves all of the credit for keeping this promise. That's because the effort to keep a nuclear weapon out of Iranian hands did not start with Obama.

"The U.S. and its allies undertook a wide range of measures long before he took office that damaged Iran's ability to produce a bomb," Bromund said. These included the assassination of nuclear scientists, a wide-ranging sanctions regime, and electronic sabotage, he said. A good example is the project known as Stuxnet. It began under President George W. Bush in 2008 and is reported to have destroyed a significant number of Iranian centrifuges, greatly slowing and complicating Iran's path to a nuclear weapon..

"While it is not easy to assess the collective effect of these (pre-Obama) measures, they certainly deserve some credit," Bromund said. He added that it's possible to say with some confidence that without such efforts, Iran's "chances of success would have been higher, perhaps significantly higher."

Critics of the nuclear deal argue that it may be able to delay Iran's acquisition of a nuclear weapon, but not preclude it forever. Even supporters acknowledge that risk. But Obama's promise was limited to keeping Iran nuclear-free during the rest of his tenure in office, and it appears that that has been accomplished. So we rate this a Promise Kept.