A week ago, the right-wing media were frenetically pushing the bogus allegation that the Obama administration was “politicizing national security.” But they dropped it as soon as Republican senators asked for an investigation, suggesting they never really believed their own claims.

The best single reason to permanently ignore the rantings of the right-wing media is not that their attacks are often easily disproven. Don't get me wrong: That's a good reason. But the best reason is that it is clear the conservative echo chamber often doesn't believe its own attacks.

Take last week's explosive allegation, first described in detail by The Weekly Standard's Michael Goldfarb, that in order to secure Sen. Ben Nelson's (D-NE) support for health care reform, the White House had threatened to close Nebraska's Offutt Air Force Base. That sent the right-wing attack machine into overdrive, with accusations of “politicizing national security” flying around and dark talk of the White House weakening U.S. national security and committing impeachable offenses.

It was an obviously ludicrous allegation (pushed, by the way, by people who worked for John McCain's presidential campaign), but it was hyped so forcefully that 20 Republican senators demanded an investigation.

Now, ordinarily, 20 U.S. senators calling for an investigation into a “scandal” the conservative media had been promoting would really set off a frenzy. Like sharks sensing blood in the water, right-wing bloggers and broadcasters would go for the kill. We'd see a constant barrage of attacks on Democrats for “blocking” an investigation into a vital matter of national security and allegations of corruption at the highest levels. They'd attack the media for not covering the alleged threat like it was Watergate, Teapot Dome, and Tiger Woods all wrapped into one. They'd be absolutely relentless.

But that didn't happen. In fact, the opposite happened: When those 20 senators sent a letter to the Armed Services Committee asking for an investigation, the right-wingers who had been so outraged promptly went silent.

On December 16, for example, an Investor's Business Daily editorial said the Obama administration's alleged threat “would amount to playing politics with our national security.” IBD hasn't mentioned the allegation since, even though it devoted its December 21 editorial to Ben Nelson's support for health care reform.

On December 15, Hot Air blogger Ed Morrissey accused the White House of “extortion” and “threatening more base closures and disruption for [sic] national security.” Morrissey wrote about Nelson twice more on December 17, again on December 19 and December 21, and once more on December 22 -- but he never again mentioned the base-closure allegation.

Last week, Glenn Beck suggested the alleged threat would constitute “high crimes” -- a reference to the “high crimes and misdemeanors” requirement for impeaching the president. Later that day, he said it “borders on treason.” But then he went quiet. (Beck has been on vacation this week, but he didn't mention Nelson during last Thursday's broadcast of his Fox News show -- his last -- or his Friday appearance on The O'Reilly Factor. And if Glenn Beck really believed President Obama had committed anything approaching “treason” or a “high crime,” you can be sure he wouldn't let a little thing like vacation keep him away from his chalkboard.)

Michelle Malkin wrote on December 15 that Nelson “is reportedly being threatened with closure of an air force base if he doesn't fall in line.” Malkin has written at least nine posts since then that mention Nelson -- but has never again mentioned the alleged threat.

RedState's Dan Perrin wrote on December 15: “The White House and Democratic Leadership in the Senate has [sic] told Senator Nelson they will close every military base in Nebraska.” That went further than anyone else, both by including the “Democratic Leadership in the Senate” in the threat and by expanding it to include “every military base in Nebraska.” But Perrin, who acknowledged the threat was not “credible,” has never again mentioned it, despite writing about Nelson on December 17, December 18, December 19, and December 20.

Even The Weekly Standard's Goldfarb has gone silent on his big “scoop” -- along with colleagues John Noonan and Matthew Continetti, who touted Goldfarb's claim on December 15 but haven't touched it since.

So what's with the sudden silence? Why isn't the right-wing noise machine that last week seemed so eager to accuse the Obama administration of “playing politics with national security” continuing the drumbeat? After all, it isn't like they've come up with any better ways to derail health care reform, which appears to be on the verge of passing the Senate (and is significantly closer to doing so than it was before Goldfarb came up with the Offutt allegation).

The simplest explanation is that they know the base-closing allegation is absolute nonsense, and they're afraid that an investigation into it would blow up in their faces.

Either that, or they take “playing politics with national security” and “treason” so lightly they just forgot all about it overnight.

Jamison Foser is a Senior Fellow at Media Matters for America, a progressive media watchdog and research and information center based in Washington, D.C. Foser also contributes to County Fair, a media blog featuring links to progressive media criticism from around the Web, as well as original commentary. You can follow him on Twitter and Facebook or sign up to receive his columns by email.