Why is the number 150 important? Because, under the terms of Bob Corker’s Senate bill, it would take only one-third of either chamber in Congress to support Obama’s deal with Iran to guarantee that it takes effect. In a constitutional system, which we used to have, the final agreement with Tehran would be regarded as a treaty and would fail to take effect unless two-thirds of the Senate voted to approve it. In our post-constitutional system, assuming Corker’s bill passes, Congress will vote first on whether to approve the deal. If they vote no, Obama can veto that “no” resolution. Then, in order to override Obama’s veto, both chambers would need to re-pass the resolution with two-thirds majorities. In other words, rather than forcing Obama to convince two-thirds of the Senate to back his deal, Corker’s bill forces the GOP to convince two-thirds of both chambers to oppose it. And now, per Greg Sargent, 150 Democrats have sent a letter to O hinting strongly that they’ll support his final deal so long as it sticks more or less to the framework that the White House announced last month. Of those 150 Dems, 145 are voting members in the House — which is exactly one-third of the chamber. Assuming that everyone who signed the letter votes with Obama on the final Iran deal and they can find one more vote somewhere in the caucus, there’s no way the House can override O’s veto. The Iran deal will take effect, even with heavy majorities in both chambers opposed to it. Like I said: Post-constitutional.

Now think about this: Democrats released this letter to Sargent this morning, before the Senate had even voted on Corker’s bill. Senate Republicans knew from this letter that adopting Corker’s scheme would all but guarantee that whatever deal Obama ended up making with Iran would end up being implemented. Voting for the Corker bill under those circumstances was tantamount to rubber-stamping O’s final agreement with Iran.

They voted for Corker anyway this afternoon, 98-1. That’s what Republican “failure theater” is all about.

The letter does not commit its signatories to ultimately supporting a final deal. But, in declaring support for seeing negotiations through — and in particular for turning the “strong” framework into a long term deal — it suggests that its signatories will likely support such a deal if it does look like the framework the parties already agreed upon (which is obviously far from a certain outcome).

“This letter reflects wide support for the agreement as outlined in the framework,” Rep. Schakowsky told me. “If there is a vote in the Congress to disapprove of the final agreement, and it is an agreement that reflects the framework, then I think we have enough votes in the Congress to sustain a veto.”…

Daryl Kimball, the executive director of the Arms Control Association, thinks the letter could also help by giving negotiators leverage in the final talks. “This will strengthen the hand of U.S. and P5+1 negotiators in the final rounds of difficult negotiations with Iran, because it reinforces the fact that the Obama administration will likely have sufficient political support from Congress to follow through on the U.S.’s commitments in the framework agreement,” Kimball says. “This expression of Congressional support for the framework should make it more likely that the negotiators can finalize the remaining details before June 30.”

In theory, if the terms of the final deal reek even more than everyone expects, some of these 145 could peel off and Boehner would have a shot at a two-thirds veto override. In practice, there’s no earthly way that Democrats would abandon O after going to the mat for him with a public pledge of allegiance like this. The text of the letter could have been written by the White House press shop:

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They’re backing whatever Obama and Kerry end up farting out because, contra what the White House has been telling the public for months, Democrats think a bad deal is better than no deal. No deal leaves war on the table as an option for dealing with Iran’s nuclear program; a bad deal, which will make an Iranian bomb more likely, takes it off the table. A bad deal is better than no deal.

As for that Senate vote on Corker’s bill, the lone no vote came from Tom Cotton. Presumably the hawks who voted yes simply gave up after McConnell refused to give any of Cotton’s or Rubio’s poison pill amendments a chance to end up in the final bill. It was Corker’s text or nothing, and Corker’s text at least gives Republican a theoretical chance to block the final deal by convincing Democrats to help them form a two-thirds majority against it. That’s another “virtue” of a post-constitutional system. If your only choices are between congressional inaction, in which case Obama’s deal definitely gets implemented, and a weird scheme like Corker’s, in which case the deal almost definitely gets implemented, you go with the latter, right? Those are the choices facing our fightin’ Republican majority these days.

Exit question: Why did Pelosi and those 150 Dems risk spooking Senate Republicans by issuing this letter today before they’d even voted on Corker’s bill? Why not wait until after the vote? I guess passage was such a sure thing that they couldn’t resist exposing “failure theater” even before it had officially taken place.