A prominent conservative political action committee is vowing to defeat any Republican senator who votes to ratify the New START nuclear arms control treaty with Russia in the lame-duck session of Congress.

The National Republican Trust PAC is making its pledge in a letter that was obtained by RealClearPolitics before it was set to be delivered on Friday afternoon.

In the letter, the PAC’s executive director Scott Wheeler writes to National Republican Senatorial Committee Chairman Sen. John Cornyn and Republican National Committee Chairman Michael Steele that the group is “fully committed” to defeating any GOP senator that votes for ratification during the lame-duck session.

“We as a country cannot allow our national defense to be greatly undermined by a President and members of a lame duck Congress who are hell-bent on redistributing America’s military advantage because of their bizarre belief that the US lacks the moral authority to be the world’s lone superpower,” the letter says. “Republicans cannot and must not participate in the sell out of our national defense merely because of political pressures applied to them by an extremist President and a liberal media.”

In the letter, Wheeler goes on to write that the group will recruit primary challengers and “will be singular in the purpose” of defeating pro-ratification Republican senators.~Scott Conroy

The good news is that I very much doubt this will discourage any of the likely supporters of the treaty. Republican Senators inclined to support New START know what the treaty actually does and doesn’t do, so it’s not as if they’re going to be forced to change positions because of this sort of nonsense. Republican voters are typically split fifty-fifty on the issue, and it’s hardly something that is going to determine the outcome of a primary race. At least two probable pro-treaty Senators are retiring (Voinovich, Gregg), Lugar and Snowe are up for re-election in 2012 but are very popular in their states, and almost all of the other vulnerable 2012 incumbents have already sided with Kyl against ratifying in this session, and most of the 2012 incumbents are staunch opponents of the treaty. Isakson is one of the more likely votes for ratification, but he isn’t up again until 2016.

Corker is one of the special targets of this campaign, and he has already hedged his support for the treaty in this session with so many qualifications that it is unlikely that he will vote to ratify. Scott Brown voted for the motion to proceed, but that is no guarantee that he will vote for the treaty. If he does, that will mean that this PAC has vowed to launch a primary challenge against exactly one beatable incumbent in a heavily Democratic state. This PAC has effectively promised to undo the results of the 2010 Massachusetts election and give back a seat to the other party, and all for the sake of enforcing a ludicrous ideological test against an obviously desirable treaty.

I can understand the impulse to challenge and expel party moderates, and if this were a general protest against the overall voting record of some of these Senators it would make some sense on its own terms. Launching a single-issue primary challenge over an arms control treaty that 70-80% of Americans support is a stunning waste of time and resources. The donors to this PAC must be pleased to know that their money is going to be thrown away for no reason.

Wheeler says that the treaty is more important than the stimulus. He’s right, but not in the way that he means it. Challenging incumbents for supporting the treaty is both substantively wrong and politically foolish. Helping to push Specter out of the party on account of his support for the stimulus bill led to the passage of health care legislation. If anti-ratification forces are successful in blocking the treaty, they will responsible for something much worse for U.S. security and interests.