Mitt Romney, the once and future presidential candidate, is the biggest gun so far to come out against the New START arms control agreement. In a no-so-subtlety titled opinion piece “Obama’s worst foreign-policy mistake” in The Washington Post, he flatly states, “[t]he treaty as submitted to the Senate should not be ratified.”

Sure, other conservative stalwarts had already jumped on New START. According to John Bolton, the former U.S. ambassador to the U.N., “there is no compelling reason for the Obama-Medvedev treaty, and there are many reasons to fear its impact.” But, Bolton, as far as I know, isn’t planning on asking for Obama’s job.

It’s a bold move for Romney. The White House has been all-high-fives over such Republican supporters as George Shultz, Howard Baker and Colin Powell.

Even in the ranks of the Senate, most of the honorable gentlemen and gentlewomen are holding off rejecting the treaty outright. Sens. Jon Kyl of Arizona and Jim DeMint of South Carolina have expressed a pretty high degree of skepticism. At best, however, most of the legislators on the right have confined themselves to demanding the White House give up more background information, demanding “reports on Russia’s compliance with a nuclear arms control treaty that expired last December,” and requesting “the record of negotiations that led to the New START agreement in a letter to President Obama on May 6.”

By coming out and saying the treaty is unacceptable as it is, Romney finds himself standing pretty much to the right of the Right.

Admittedly, it’s a hard position to defend on a bumper sticker. Who would be against cutting nuclear weapons?

Well, no one — and that’s pretty much Romney’s point. By constraining U.S. missile defenses, America loses a potent argument for dissuading enemies that nuclear-tipped ballistic missiles are weapons worth having.

In the case of Russia, there won’t be much cutting. New START allows for higher levels of weapons than would have been permissible under the combination of START and the old Moscow Treaty. These treaties also had better verification measures. Furthermore, Russia can actually build more delivery systems under the agreement, and there are no limits on modernization or tactical nuclear weapons.

It might not fit on a bumper sticker, but it’s hard to argue with Romney’s conclusion: “By all indications, the Obama administration has been badly out-negotiated. Perhaps the president’s eagerness for global disarmament led his team to accede to Russia’s demands, or perhaps it led to a document that was less than carefully drafted.”

Of course, others have argued: “What’s the big deal? At least it’s something” Well, it is a big deal if you believe that New START is a bad deal and the U.S. could and should negotiate a better one; that it is a bad precedent to let the Russians and the world think we are patsies; that it’s bad to hamstring the future of missile defense; and that it’s wrong to sign a treaty that doesn’t actually advance U.S. interests.

It’s a big deal to Romney, obviously. Maybe he thinks standing in a lonely place will set him apart from the pact. He has done that — for now. Perhaps when others start to take a harder look at what New START might mean for the future security of America’s and its allies, he will get a lot more company.