Energy Secretary Ernest Moniz — the wild-haired scientist who has emerged as a pivotal figure in selling the Iran deal to Democrats on Capitol Hill — is taking new steps today to shore up enough Democratic support to ensure that if President Obama vetoes a Congressional measure disapproving of the agreement, that veto will be sustained.

And there’s a reasonable chance Moniz’s latest move might work.

Back in May, we reported that 150 House Democrats had signed a letter backing the initial Iran nuclear framework released at the time — which was significant, because that number of Dems would be enough to sustain an Obama veto of any Congressional measure disapproving of the deal. But it wasn’t certain — and it still isn’t certain — that all those Dems would support the final deal in the end.

Now Energy Secretary Moniz  has written a letter in response to all those 150 House Dems, explaining to them that the final Iran accord fulfills their original stipulations in that initial letter, and then some.

Here’s why this is significant: If this letter proves persuasive to all of those Democrats, who were inclined towards the deal to begin with, the Iran deal will all but certainly move forward.

The letter, which was sent over by a source, responds in detail to the initial missive signed by all those Democrats. That initial letter described the framework reached in the first round of negotiations as “strong,” and called on the administration to continue working towards a “verifiable, enforceable, diplomatic solution in order to prevent a nuclear-armed Iran.”

In response, Moniz’s letter basically says: You asked for it; you got it. From the letter:

I strongly share your commitment to a “verifiable, enforceable diplomatic solution in order to prevent a nuclear armed Iran.” As a negotiator alongside Secretary Kerry during the months leading to the Joint Comprehensive Plan of Action (JCPOA), I wanted to let you know how the critical objective you supported in response to the Lausanne framework was further strengthened in the final JCPOA.

Moniz’s letter goes on to argue that “there are additional important and specific commitments” in the final deal that have “strengthened” the original framework that all of those Democrats supported in May. It then runs through all the specifics of the deal.

While the arguments in the letter are the ones we’ve already been hearing from the administration, the letter represents an intensification of the administration’s pitch directly to the House Democrats who backed the original framework. This is notable, because foes of the deal had reportedly thought they could peel away some of these Democrats — despite their support for the original framework — by sowing doubts about the specifics of the final deal, and by running ads back in their districts pressuring them to oppose it.

As of today, not one of those 150 House Dems has come out against the deal, though there are plenty who have not yet declared official support.

All this comes after a handful of key Senate Democrats also came out for the deal this week, making it less likely that opponents can muster the two-thirds they’d need to override Obama’s veto in the upper chamber, too. Obviously the White House would prefer to sustain the veto in both chambers But the ultimate firewall against a veto override has  long been seen to reside in the House.

Which explains why the administration today is intensifying its efforts — with Moniz’s letter — to lock down that firewall, and with it, an assurance that the deal will go forward.