As U.S. lawmakers today begin debating the agreement the United States and five other nations have reached with Iran to limit its nuclear weapons program, the only physicist serving in Congress has announced he will support the deal.

“After carefully weighing all the options and possible outcomes, I do believe that voting for this deal will make it less likely that Iran will develop nuclear weapons,” Representative Bill Foster (D–IL) said yesterday at a Washington, D.C., press conference. “And voting against this deal, with no better options in sight, makes the potential for Iran to develop a nuclear weapon more likely.”

Whether Iran ultimately obtains a nuclear weapon is as much a matter of physics as it is of politics, Foster suggested at Tuesday's announcement. That’s why he has been analyzing the science underpinning the deal—in addition to the politics—since the proposed agreement was announced this past July. Now, after 15 “lengthy” briefings with U.S. Department of Energy (DOE) scientists and other technical experts, Foster says his support “is determined not just by trust, but by science.”

The congressman holds a physics Ph.D. from Harvard University and spent more than 2 decades as a particle accelerator designer at Fermilab, a DOE national laboratory in Batavia, Illinois. Because of his training and experience, Foster emphasized that he felt “a special responsibility” in reviewing the proposed agreement, especially concerning its more technical aspects such as the transformation of Iran’s Arak reactor to render it incapable of producing large amounts of weapons-grade plutonium.

Foster noted that his physics background and experience managing technical projects had helped him analyze whether the deal would successfully block the multiple paths the Iranians might take to create a nuclear weapon. “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, making sure we have all the leaks plugged,” he said.

At the press conference, the congressman was flanked by U.S. Secretary of Energy Ernest Moniz, one of the key negotiators of the agreement, and Richard Garwin, a physicist who helped develop the first hydrogen bomb. Garwin recently co-wrote a letter to President Barack Obama supporting the agreement along with 28 prominent scientists and engineers, including Rush Holt, who signed as an individual but is also the chief executive officer of AAAS (publisher of ScienceInsider).

“I am here today to add my name to that list of 29 scientists and engineers who have endorsed the deal and the growing number of members of Congress who will be voting in favor of it,” Foster said.

Although a majority of both houses of Congress—which are controlled by Republicans—are expected to support a measure opposing the deal, analysts predict it will survive. That is because opponents in Congress have not mustered enough support to override a presidential veto, which requires two-thirds of the votes in each body. (President Obama has signaled that he would veto such a measure if it reached his desk.) It is still not clear, however, whether the Senate will actually vote on an Iran bill; 42 Democrats have said they support the deal, potentially denying opponents in the Senate the 60 votes needed to end debate and bring the issue to a vote.