He’s blinding them with science.

Or intellectually charming them anyway. That’s how Energy Secretary Ernest Moniz seems to be winning fans in the difficult fight to sell the Iran deal on Capitol Hill, even as skeptical lawmakers reserve plenty of vitriol for his partner on the journey, Secretary of State John Kerry.

Moniz, a nuclear physicist with mad-scientist hair, has already been credited as the administration’s secret weapon in the lengthy negotiations to secure an Iran deal that will prevent the rogue country from securing a nuclear weapon. The deal depends heavily on inspections and verification processes to ensure the Islamic Republic does not enrich fissile materials past thresholds acceptable for peaceful uses.

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Now, as the House Foreign Affairs Committee prepares to grill Cabinet members on Iran Tuesday morning, the administration is counting on Moniz — a longtime MIT professor who served as Energy under secretary in the Bill Clinton administration — to sell it.

“He’s certainly more technical than I am, let’s put it that way. I barely made it through high school chemistry,” said Rep. Peter King (R-N.Y.), following a closed-door briefing Kerry, Moniz, and Treasury Secretary Jack Lew held with House members last week. King has been fiercely critical of the Iran deal, and of Kerry’s role in both negotiating and promoting it.

“I thought his tone was very good,” King added of Moniz — high praise from a congressman who only about a minute before had declared aspects of Kerry’s tone “very offensive.”

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Moniz can certainly lapse into the technical talk with aplomb — and when he gets to talking about the half-lives of isotopes and the detection technologies that will be deployed to survey Iran’s suspected nuclear activities, he can leave his audience in the dust.

But in the two years since Moniz became Energy Secretary, lawmakers have far more often noted and applauded the former professor’s natural ability to translate complex scientific concepts into digestible terms.

“I’ve worked with him a lot, because I work on a lot of energy issues,” said Sen. John Hoeven (R-N.D.), a critic of the Iran deal. “I mean the guy is a nuclear physicist — he can be very technical if he wants to be. But he’s also careful to put things in layman’s terms.”

Moniz is also aided by a degree of freedom that comes from operating somewhat out of his natural element.

Moniz is a product of MIT, not years on the campaign trail — and thus appears more comfortable than many other administration officials and lawmakers going off script in his public appearances, occasionally even having some fun with the political side of the game.

For example, when testifying about the Iran deal at a heated Senate Foreign Relations Committee meeting last week, Moniz managed to cut tension in the room between Kerry and Chairman Bob Corker (R-Tenn.), who had just charged that Kerry had been “fleeced” on the Iran deal, with a single quip.

It came amidst his explanation of the International Atomic Energy Agency’s advanced enrichment monitoring capacities.

“Things like real-time enrichment monitoring, which I might say is a technology developed by our Department of Energy laboratories,” Moniz said, looking up and grinning widely at Corker to add: “In this case, by the way, Oak Ridge” – a major government nuclear testing and development facility in Tennessee – “played a major role, Mr. Chairman.”

Corker, for his part, also can’t help but speak well of Moniz. When telling reporters earlier this week that Kerry “seemed a little defensive” trying to advocate for the Iran deal on the Sunday morning shows, he raised the Energy secretary as a point of comparison.

“Moniz does not present himself in that manner, by the way,” Corker said. “He’s not defensive.”

Not even, apparently, when some brave soul decides to go head-to-head with Moniz on matters of science.

Sen. Ron Johnson (R-Wis.) — who ran a major plastics company before coming to Congress — was the only one to try to challenge Moniz on a scientific question during the lengthy hearing on the Iran deal. He didn’t drill down into the mechanics of reactors or enrichment surveillance, but he did ask Moniz why he wasn’t speaking more about electromagnetic pulses in the context of the Iran deal, and why he wasn’t familiar with the substance of a 2008 report on the issue.

Electromagnetic pulse attacks are seen as a disruptive threat to the country’s electrical grid; the threat, when it comes up for discussion, is more often raised by conservatives.

Moniz largely refrained from retorting, instead apologizing for not having read the report in question.