While you might explain this outcome in purely partisan terms — the Republicans all oppose the deal because it’s Barack Obama’s, and nearly all the Democrats stand behind their party’s leader — the outcome on the Democratic side is still notable, because it represents a triumph over the kind of attack before which Democrats have so often run frightened in the past.
If you’re too young to remember the time before the Iraq War turned into a disaster, you may not realize the state of constant fear Democrats used to live in when it came to national security. Particularly since Ronald Reagan’s presidency, Republicans were always ready to ridicule them as being “soft” — soft on defense, soft on the communists, soft on anything involving foreign threats. After 9/11, this attack went into a higher gear, as did Democrats’ fear that any show of softness would instantly be met with, “Why are you on the terrorists’ side?” and “Why don’t you support our troops?”
That’s why it was widely understood among Democrats in 2002 that no one with any national ambitions could vote against the Iraq War when the drums were beating so loudly. With only one exception (Florida’s Bob Graham), all the Senate Democrats who would run for president in 2004 or 2008 voted Yea, including Hillary Clinton, Joe Biden, and John Kerry. Everyone assumed that was the only safe vote to take. And when Kerry became the party’s nominee in 2004, he centered his entire campaign on the story of his service in Vietnam, on the theory that a couple of chicken hawks like George Bush and Dick Cheney would never attack the patriotism of a war hero (that theory proved to be mistaken).
The failure of the Afghanistan and Iraq wars enabled Democrats to feel that they didn’t have to constantly bend over backward to show that they’re tough, when toughness is what cost the country so much in recent years. But the Iran debate put that belief to the test. That’s because for Democrats, there really is some risk in supporting this deal.
If the agreement proves to be a failure — let’s say that Iran manages to conduct a nuclear weapons program in secret, then announces to the world that they have a nuclear weapon — it will indeed be front-page news, and the Democrats who supported the deal might suffer grave political consequences. So in order to vote yes, they had to look seriously at the deal and its alternatives, and accept some long term political peril.
By contrast, there probably is less long term risk for Republicans in opposing the deal.
It’s true that if the deal does achieve its goals, it will be added to a list of things on which Republicans were spectacularly wrong, but which led them to change their opinions not a whit. The Iraq War didn’t have an appreciable impact on their views about the wisdom of starting new military engagements in the Middle East. Nor did their failed predictions about Bill Clinton’s tax-increasing 1993 budget (they all said it would cause a “job-killing recession” and every one of them voted against it) and George Bush’s tax cuts (they said the cuts would lead to an explosion of economic growth) alter their views on what effect tax increases have on the economy.
But if the deal works as intended, what will be the outcome be? Iran without nuclear weapons, of course, but that is a state of being rather than an event. There will be no blaring headlines saying, “Iran Still Has No Nukes — Dems Proven Right!” Five or ten years from now, Republicans will continue to argue that the deal was dreadful, even if Iran’s nuclear ambitions have been contained.
My guess is that now that the practical fight over this deal is essentially over, Republicans won’t bother to keep arguing about it too much. In the primaries, the presidential candidates will throw in a perfunctory line or two in their speeches about how awful it is, how they’ll tear it up on their first day in office, and how it shows that Democrats are weak. But with the deal now facing the lengthy task of implementation and no substantive victory possible for them, they won’t see much to be gained in harping on it. But they’ll probably continue to believe that calling Democrats weak on national security is tremendously effective, even if the Democrats themselves aren’t as afraid of that attack as they used to be.