The Wall Street Journal reports: As the White House ramps up its campaign to sell its Iran nuclear deal to a skeptical Congress, a shaggy-haired scientist is proving to be its best asset on Capitol Hill.

Both Republicans and Democrats called Energy Secretary Ernest Moniz, a former Massachusetts Institute of Technology physics professor, the administration’s most credible source of information on the accord reached this week aimed at curbing Iran’s nuclear program and the negotiations that produced it.

“He’s by far been the best witness, the best person to talk to,” said Senate Foreign Relations Committee Chairman Bob Corker (R. Tenn.). On Thursday, Mr. Corker said Mr. Moniz would testify at the committee’s first hearing on the final deal next week, along with Secretary of State John Kerry and Treasury Secretary Jack Lew.

The agreement reached Tuesday in Vienna puts strict limits on Iran’s nuclear program for the next decade that are designed to keep Tehran from being at least 12 months away from amassing enough nuclear fuel for a bomb. In exchange, the U.S., the European Union and the United Nations will lift economic sanctions on Iran.

Mr. Moniz, 70 years old, played a key role over the months of talks that led to the accord between Iran and six global powers. In particular, he had a string of one-on-one technical discussions with Ali Akbar Salehi, now chairman of the Atomic Energy Organization of Iran. Mr. Salehi studied at MIT in the 1970s, when Mr. Moniz taught at the school, though they didn’t meet there.

“It’s extraordinarily fortunate that at this moment in time we have, in the cabinet and on the negotiating team, an honest-to-goodness nuclear physicist who knows this stuff,” said Sen. Angus King (I., Maine). [Continue reading…]