Rep. Bill Foster, the only member of Congress with a PhD in physics, announced his support for the Iran nuclear agreement Tuesday, a day before the House begins its official debate leading up to a vote on whether to disapprove the deal.

Joining Foster in a press conference were Energy Secretary Ernest Moniz, one of the top negotiators of the agreement, and Richard Garwin, a physicist who helped develop the first hydrogen bomb and the lead signer of a letter last month from 29 scientists to President Obama supporting the deal.

Foster said his background in physics – including a doctorate from Harvard and a two-decade career at Fermi National Accelerator Laboratory – made him feel a “special responsibility” to weigh the agreement carefully, and gave him a unique approach to that review. His endorsement included not just an analysis of the politics involved but of technical aspects of Iran’s nuclear program.

“After carefully weighing all of the options and possible outcomes, I do believe that voting for this deal will make it less likely that Iran will develop a nuclear bomb, and voting against this deal with no better options in sight makes the potential for Iran to develop a nuclear weapon more likely,” the Illinois congressman said.

“My support of this agreement is determined not just by trust, but by science.”

Foster is now among the more than 100 House Democrats who support the deal, though more than a dozen of his party colleagues and all Republican members of the House oppose the agreement. That means there are easily enough votes to pass a resolution of disapproval later this week, though that tally will be moot in light of Senate support that guarantees the deal’s survival.

Foster said he held 15 briefings on the issue, many of which were “lengthy” sessions with technical experts who supported the negotiating team. He broke down his backing into four key technical aspects.

First, he said the notion that Iran would have the ability to self-inspect its nuclear facilities – an argument used by opponents of the deal – is “simply not true.” Second, he said that while the 24-day period to inspect potentially undeclared nuclear sites was not ideal, there was “limited operational difference” between 24-hour and 24-day time frames. Third, he said his analysis confirmed the Obama administration’s estimate of a one-year breakout time for the world to respond if Iran resumes its nuclear program. (Foster told RCP in July that the breakout time was one of the key issues he was considering in his review.) Last, he talked about the importance of monitoring Iran’s program given the short “weaponization time,” the gap between when Iran would possess nuclear material and when that material could be developed into a weapon once some of the deal’s parameters end in 15 years.

Moniz, who has known Foster for nearly two decades and is himself a nuclear physicist, became the Obama administration’s MVP when it came to lobbying members of Congress on the technical aspects of the agreement. He praised Foster’s approach during the press conference Tuesday.

“I have to give Bill enormous credit for the way he has dug in,” Moniz said. “I can vouch for his 15 briefings, I can vouch for the time he has taken, not begrudgingly on our side, of our scientists. ... I think it really is something noteworthy when, again, my old FermiLab friend dug into this and has come out, I would say, endorsing the science that underpins this agreement. And we always said science underpinning it is the origin of the confidence that many of us should have.”

Foster said that one of the advantages of having a background in physics is that he was able to analyze the various paths Iran might take to creating a nuclear weapon and determine whether the deal successfully blocked each of those paths.

“I’ve done significant project management of technical projects,” Foster said. “So I went into this putting myself in the mindset of a nuclear proliferator in Iran and saying, ‘What if I try that? If we find this is impossible or blocked by the agreement, what are the alternatives?’ So you go through these ‘what if’ questions and make sure we had all the leaks plugged. [That] is something where I think we had a unique capability.”