House Democrats will play a key role in whether the Obama Administration can get a deal with Iran. Under the Corker-Cardin deal on the Corker Congressional review legislation, if a third of the House or a third of the Senate were willing to sustain a Presidential veto of Congressional legislation against the deal, that would be sufficient to block Republican efforts to kill the deal.
Even if all House Republicans oppose the President if it comes to a vote (by no means guaranteed, but certainly plausible), that means roughly 3/4 of House Democrats supporting the President would be sufficient to protect the deal.
To be precise, there are 435 seats in the House, so a bloc of 435/3+1 = 146 House Members would be sufficient to protect the deal. There are 188 Democrats in the House. So roughly 3/4 (78%) of House Democrats have to support the President to guarantee House protection of the deal. If no more than forty-two House Democrats defect to the Republican side, the advocates of diplomacy are dancing in the street. But if forty-three House Democrats defect to the Republican side, diplomacy advocates will have to start calling in chits with the Ron Paul people (the father, not the prodigal son.)
House Democratic Minority Leader Nancy Pelosi is strongly backing the President on Iran diplomacy. But that's no guarantee that three-fourths of House Democrats will back the deal. For example, House Democrat Alan Grayson is attacking the negotiations by trying to introduce issues that are outside the scope of the talks and by trying to set an impossible "unicorns and ponies" standard for a "good deal."
So, what would be really useful right now would be a show of strength by House Democrats in support of diplomacy.
Fortunately, Illinois Democrat Jan Schakowsky (you may recall that she skipped Netanyahu's anti-diplomacy speech to Congress) is circulating a letter to her colleagues in support of diplomacy. Wouldn't it be grand if we could get 146 House Democrats to sign the Schakowsky letter? You can weigh in online here; if you happen to be represented by a Democrat in the House, you can call them here.
Here is a video - made by a Grayson supporter - of Alan Grayson attacking the scope of the Iran talks at a fundraiser in Santa Monica.