The trains run on time.
The Iran nuclear deal must pass. And all sides know that and accept it. You wouldn't know it to hear them talk, but it's all a kabuki dance put on for the rubes at home. Ever since it came out that this was a five nation deal, they (the American Politicians) knew it was a must pass item. So, they set it up so they can vent and beat their chests and write to their constituents that they tried to stop Emperor Obama's Oh So Terribly Bad Deal with Iran from going through, but darn him and his magic African-American mojo!
This is why Sen. Grassley passed his resolution, so the Legislature can say, "NO!" but not have it stick. Of course President Obama has enough Senators to sustain his veto (I'm not sure they counted on him having enough to filibuster their "NO!" vote though, that'll take some steam out of them).
This was the way it was always going to be. The GOP knows the damage they'd take if they really did what they could to scuttle the deal. See, without the US, the deal will go into effect anyway. It's only that the US will be holding the bag when it comes to sanctions. And if we did end the deal, Iran will get the bomb, probably within a year.
But the GOP and conservatives 1) can't support anything President Obama does (they've tied themselves into rhetorical knots over that) and 2) can't appear to be "caving in" to Iran (because their rhetoric positioned them there as well).
So, they'll vote no (if they can). And when the President vetoes their disapproval they'll stamp and scream at Emperor Obama and his mad executive ways, all while relaxing a little that no one will call them on their complicity.
But what could they do, I hear some people ask.
Exactly what they did when they didn't like other Obama Executive Orders/Actions. Sue. Get a court injunction against President Obama from carrying out the terms of the agreement.
Notice the chorus of crickets when it comes to using a tactic they've successfully used twice and unsuccessfully used once. There has been no talk of a lawsuit (even if it would cause a Constitutional Crisis, a real one, not the fake ones they've been parading about). The would have standing, the President is going against the direction of some of the sanctions which were passed by the Legislature (even if the final actions were up to the Executive branch).
And here's the nuclear option (to coin a phrase), enact more sanctions against Iran. That right there, in and of itself would violate the agreement. And I bet they could get a veto proof majority for it as well. There was talk about that last Spring. Heard anything of it lately? Of course not.
Because this deal must go through.
That doesn't mean the GOP won't try and spin it in a negative sense (just like they've been trying to do with Cuba). But they know without this deal, Iran has the bomb in less than a year, and Iran remains belligerent.
With the deal, Iran won't be able to get the bomb (as long as everything works properly and everybody plays ball) for over 13 years. A decade is a forever in diplomacy world. Thirteen years means three Presidential elections here, and at least two in Iran. Over a decade of renewed interest in world affairs and Iran will probably be a very different country than it is now. If we can navigate the waters between Iran and Saudi Arabia for the next decade, it will be a very different world indeed.