Teeth forever gnash over the “liberal media” tale, which portrays reporters conniving in back-alleys to undermine the American Way — tutored, of course, by a sinister Old Gray Lady, otherwise known as The New York Times.

One problem: It’s all a fable, told so often it’s woven into the national lore. Dick Polman exposed it in a December column with his usual snap and wit. He’s always worth the read – even when he makes you scream – but his valiant effort has the feel of Sisyphus shoving his boulder.

Some highlights:

First, why did the supposedly “liberal” Washington Press Corps fawn over Ronald Reagan?

Second, why did the liberal cabal ceaselessly hammer President Clinton over his supposed involvement in the “Whitewater Affair,” even though repeated investigations found no “there” there?

Third, why did the The Old Gray Lady sabotage President Obama’s plans to close Guantanamo’s prison when it rushed to publish information on inmate recidivism rates? It turns out the leaker’s leak was false.

I’ll quote Polman himself on Highlight Number Four: “But worst of all is the ‘liberal’ media’s failure to vet George W. Bush’s march to war in Iraq – most notably, its trumpeting of bogus leaks from pro-war sources who claimed to know about Saddam WMDs. As one observer later remarked, ‘The national press corps was probably too deferential to the White House….In this case, the ‘liberal media’ didn’t live up to its reputation. If it had, the country would have been better served.’ So wrote Scott McClellan, press secretary for George W. Bush.”

And so it goes unto the very present: In early December, The Times gift-wrapped campaign ammo for Republican candidates when it said San Bernadino terrorist Tashfeen Malik “talked openly on social media about her views on violent jihad.” Except that Malik had only written private messages. Under a pseudonym. In Urdu.

The beat drums on. Ted Cruz recently hid behind the fable in a GOP debate and evaded a question. The crowd cheered while the boulder rolled and Sisyphus sighed.

Perhaps the myth’s resilience lies in its age. It hearkens, at least, to the agnew on the warpathNixon administration, when Vice President Spiro Agnew played a Charlie McCarthy doll to the president’s Edgar Burgen and articulated his boss’s press paranoia in November, 1969: “When the President completed his (recent) address — an address, incidentally, that he spent weeks in the preparation of — his words and policies were subjected to instant analysis and querulous criticism. The audience of 70 million Americans gathered to hear the President of the United States was inherited by a small band of network commentators and self-appointed analysts, the majority of whom expressed in one way or another their hostility to what he had to say.”

Agnew had barely warmed up: “When Winston Churchill rallied public opinion to stay the course against Hitler’s Germany, he didn’t have to contend with a gaggle of commentators raising doubts about whether he was reading public opinion right, or whether Britain had the stamina to see the world — the war through. When President Kennedy rallied a nation in the Cuban missile crisis, his address to the people was not chewed over by a roundtable of critics who disparaged the course of action he’d asked America to follow.”

The right has been working the ref ever since, invoking the “liberal media” conspiracy like a squid sprays ink. Never mind the burgeoning Murdoch empire and talk radio’s right wing lurch – and never mind that a sea of political correctness swept away liberalism from the political landscape, at least in its FDR-Truman-JFK-LBJ form. The “media” now bends over backwards to prove its a-liberal “objectivity.” The consequence: muck-raking has gone the way of the old Knight Ridder and Times Mirror companies, with ProPublica remaining as one of the last bastions of investigative reporting. Most newsrooms are now skeletons of their former selves due to budget cuts, ruled by haggard refs.

Even Sisyphus has fled the scene.