Ever since the Senate Foreign Relations Committee approved the U.S.-Russia New START nuclear-reductions accord this afternoon, I’ve received statements from President Obama, Vice President Biden, Secretaries Gates and Clinton and Senator Kerry. All of them are cheering the vote, in order to get the press to write about the Big Victory they recorded today. And indeed: it’s a step forward for a treaty that any sensible person would have to conclude deserves ratification.

The trouble is that none of these statements actually explain, hint at or otherwise indicate how to get 67 votes in the Senate for the treaty. Max Bergmann does a whip count and finds that it’s plausible to pass New START in the next three weeks, before Congress adjourns for the election and the Democrats lose shitloads of House and Senate seats. After that, when the Senate fills up with ever-more hostile Republicans who will want to ride their victories into a wave of obstruction, much as anti-Bush Democrats did after 2006, the Senate math becomes somewhere between horrible and terminal for the treaty.

It’s basically in Harry Reid’s hands. Or, rather, the administration and the Democratic Senate leadership could still mishandle moving the treaty through the Senate in the next three weeks, but if Reid doesn’t schedule the vote, it’s all over. Kerry has already mused about voting on the treaty in the lame-duck session. But why would any Republican go along with that proposal? If the administration wants to give up even more money for modernizing the nuclear stockpile — the key deliverable GOP objection to the treaty — it can promise that as easily now as it can after November, when it will be in a weaker position.

Who knows, maybe the GOP thinks it can win the Senate outright — not implausible — and so then it can just write and pass legislation upping the modernization budget without passing New START. All these scenarios grow more plausible for the GOP after the congressional session.

What’s Reid going to do, now that the committee’s reported the treaty out? Josh Rogin had a quote the other day from an anonymous GOP aide that rang true: “Are they drunk? Why would Harry Reid spend any floor time on this, it’s just not going to help any Democrat get elected.” Unless the Obama administration suddenly learned how to control the Senate — or even the Senate Democratic caucus — than the guy’s got a point.

Here’s the basic political problem. There is no constituency in the United States electorate for arms control in any significant number. Suspicion that the U.S. is getting rolled by any foreign accord is so high that even if a treaty is manifestly in the U.S. interest, its advocates still have to defend it against easy demagoguery. Throw in “Nuclear Treaty With Russia” and popular fears compound. And there’s no counter-coalition to mobilize support in favor of the thing. So you have to depend on elite maneuvering, which is always politically brittle. Senators facing tough elections in their home states are not going to want to spend time defending their votes on “controversial” treaties, especially if all they’ve got to say about them is, “You’re wrong, Guy At The Senior Center, because a Republican Secretary of State you’ve barely heard of told me the treaty is fine.” Like, oh, Harry Reid, for instance.

Put it a different way. At a lunch event the other day, an astute reporter asked Ellen Tauscher, the undersecretary of state for arms control, why any senator had to fear voting against New START. Her answer, as best I understood it, was that Senators are not going to want to tell their constituents that the U.S. didn’t have visibility into the Russian nuclear arsenal, which is a consequence of not passing the treaty. And that’s probably the best argument-from-fear/Senatorial self-interest in favor of New START. But does that sound to you like an argument that mobilizes votes?