‘STARTING’ TO SOUND INCOHERENT…. Even by the low standards of Senate Republicans, watching several leading members threaten to derail New START ratification over “Don’t Ask, Don’t Tell” repeal was astonishing. National security policy should never be in the hands of petty children, and yesterday’s floor debate reinforced the worst fears about GOP priorities and judgment.

But the DADT hostage strategy wasn’t the only angle to the debate that made it such a humiliating display. We also heard nonsense from the likes of Sen. Jim DeMint (R-S.C.), who said the treaty to reduce nuclear stockpiles will actually increase the number of nuclear weapons. Why? Because the voices in his head told him that made sense.

Some ridiculous arguments were even more problematic.

In a long floor speech during Senate deliberations on ratifying the New START treaty, Sen. John McCain (R-AZ) assailed the treaty for supposedly containing language to weaken the United States’ ability to implement missile defense systems. McCain cited several parts of the treaty, but focused on language in the preamble, claiming that Russia will “surely” use it to “try to keep us from building up our missile defenses.”

Yet analysts have confirmed that this is a misinterpretation of the clause; not only is the preamble non-binding, but in addition the clause in question is merely a statement of widely-recognized fact on the interrelationship between offensive and defensive missile defense systems.

McCain has absolutely no idea what he’s talking about. This isn’t a subjective matter, where reasonable people can come to different conclusions shaped by perspective and opinion; McCain is just completely wrong — the preamble is non-binding, and it simply describes the existing reality. McCain said the language will hinder missile defense efforts going forward, but the U.S. general in charge of missile defense says that’s backwards.

Reality notwithstanding, a growing number of Republicans rallied behind McCain’s recommended changes to the preamble, despite the fact that the language is non-binding, and despite knowing that approving the amendment would necessarily kill the treaty.

In all likelihood, McCain’s proposed changes will fail — there’s nowhere near a majority prepared to embrace it. The problem, though, is that it becomes another excuse for conservative senators to scuttle the treaty, blow off the demands of military and diplomatic leaders, and undermine U.S. foreign policy.

At this point, the head-count is looking shaky. To ratify, nine Senate Republicans would have to do the right thing, but at this point, I only see seven firm “yes” votes — Bennett (Utah), Brown (Mass.), Collins (Maine), Lugar (R-Ind.), Murkowski (R-Alaska), Snowe (Maine), and Voinovich (Ohio).

This one’s going to be tight, and I suspect the White House will be pushing next week as hard as it can. For a recap of the administration’s case, check out President Obama’s weekly address this morning.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.