WHEN ELDER STATESMEN NO LONGER HAVE THEIR PHONE CALLS RETURNED…. A couple of weeks ago, President Obama, commenting at the White House on the pending arms control treaty with Russia, noted, “It is a national security imperative that the United States ratify the New Start treaty this year. There is no higher national security priority for the lame-duck session of Congress.”

More interesting than the comments, though, were the three men flanking the president at the time: Brent Scowcroft, James Baker, and Henry Kissinger, all veterans of modern Republican presidents, and members in good standing of Republican Foreign Policy Elder Statesmen, at least by the standards of the Republican establishment.

The point Obama and his team wanted to emphasize, of course, is that this treaty enjoys broad bipartisan support, just so long as one overlooks the Senate Republican caucus. It didn’t matter; the GOP votes that count are the ones that refuse to even consider the consequences of their conduct.

There was a time, not too long ago, that the political world would look to these proxies as evidence of merit. If Lugar, Scowcroft, Kissinger, James Baker, Reagan Secretary of State George Schultz, Reagan Chief of Staff Kenneth Duberstein, Reagan Chief of Staff Howard Baker, and Colin Powell endorsed a treaty related to national security — and all of these Republicans have urged ratification of New START — it stood to reason that the measure would enjoy enthusiastic Republican backing. When six former secretaries of state and five former secretaries of defense from both parties; the chairman of the Joint Chiefs of Staff; seven former Strategic Command chiefs; national security advisers from both parties; and nearly all former commanders of U.S. nuclear forces were all on the same page — as they are now on New START — the proposal on the table would fairly be described as a “no-brainer.”

But that was before. Before what, exactly? Well, before the contemporary Republican Party became the contemporary Republican Party. Now, figures are left to search in vain for someone GOP senators might actually listen to.

Sen. Susan Collins (R-Maine), who has reserved judgment on how she will vote until the resolution comes to the floor, said it could make a difference if Obama could get George H.W. Bush and George W. Bush, both former presidents, to appear with him in support of the New Strategic Arms Reduction Treaty, or New START. […]

“It would be wonderful if President [George H.W.] Bush would come out for the treaty. That would be so powerful and definitely help,” Collins said in a telephone interview last week.

Really? All of these other Bush administration officials endorsing the treaty isn’t quite enough to send a signal about the measure’s merit?

Jacob Heilbrun recently explained that the GOP’s handling of this debate offers us a chance to watch “the decline and fall of the Republican foreign-policy establishment.” Ordinarily, sentences that include “Republican,” “establishment,” and “fall” might sound like an encouraging development, but in this case, it’s really not — the old-guard GOP foreign-policy establishment were the only folks left in the party still in touch with reality.

Their judgment is hardly unimpeachable — cough, Iraq war, cough — but they nevertheless offered at least some reasonable pushback to neoconservatism and the blind, knee-jerk partisanship that dominates Republican Party thinking.

Their influence, however, has disappeared. Republican policymakers are aware of the foreign policy old guard, but they prefer to ignore its members. It’s an important development in the growing immaturity of GOP politics in the 21st century.

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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.