So now we have it: what appears to be hard, irrefutable evidence of Rupert Murdoch's ultimate and most audacious attempt – thwarted, thankfully, by circumstance – to hijack America's democratic institutions on a scale equal to his success in kidnapping and corrupting the essential democratic institutions of Great Britain through money, influence and wholesale abuse of the privileges of a free press.

In the American instance, Murdoch's goal seems to have been nothing less than using his media empire – notably Fox News – to stealthily recruit, bankroll and support the presidential candidacy of General David Petraeus in the 2012 election.

Thus in the spring of 2011 – less than 10 weeks before Murdoch's centrality to the hacking and politician-buying scandal enveloping his British newspapers was definitively revealed – Fox News' inventor and president, Roger Ailes, dispatched an emissary to Afghanistan to urge Petraeus to turn down President Obama's expected offer to become CIA director and, instead, run for the Republican nomination for president, with promises of being bankrolled by Murdoch. Ailes himself would resign as president of Fox News and run the campaign, according to the conversation between Petraeus and the emissary, K T McFarland, a Fox News on-air defense "analyst" and former spear carrier for national security principals in three Republican administrations.

All this was revealed in a tape recording of Petraeus's meeting with McFarland obtained by Bob Woodward, whose account of their discussion, accompanied online by audio of the tape, was published in the Washington Post – distressingly, in its style section, and not on page one, where it belonged – and, under the style logo, online on December 3.

Indeed, almost as dismaying as Ailes' and Murdoch's disdain for an independent and truly free and honest press, and as remarkable as the obsequious eagerness of their messenger to convey their extraordinary presidential draft and promise of on-air Fox support to Petraeus, has been the ho-hum response to the story by the American press and the country's political establishment, whether out of fear of Murdoch, Ailes and Fox – or, perhaps, lack of surprise at Murdoch's, Ailes' and Fox's contempt for decent journalistic values or a transparent electoral process.

The tone of the media's reaction was set from the beginning by the Post's own tin-eared treatment of this huge story: relegating it, like any other juicy tidbit of inside-the-beltway media gossip, to the section of the newspaper and its website that focuses on entertainment, gossip, cultural and personality-driven news, instead of the front page.

"Bob had a great scoop, a buzzy media story that made it perfect for Style. It didn't have the broader import that would justify A1," Liz Spayd, the Post's managing editor, told Politico when asked why the story appeared in the style section.

Buzzy media story? Lacking the "broader import" of a front-page story? One cannot imagine such a failure of news judgment among any of Spayd's modern predecessors as managing editors of the Post, especially in the clear light of the next day and with a tape recording – of the highest audio quality – in hand.

"Tell [Ailes] if I ever ran," Petraeus announces on the crystal-clear digital recording and then laughs, "but I won't … but if I ever ran, I'd take him up on his offer. … He said he would quit Fox … and bankroll it."

McFarland clarified the terms: "The big boss is bankrolling it. Roger's going to run it. And the rest of us are going to be your in-house" – thereby confirming what Fox New critics have consistently maintained about the network's faux-news agenda and its built-in ideological bias.

And here let us posit the following: were an emissary of the president of NBC News, or of the editor of the New York Times or the Washington Post ever caught on tape promising what Ailes and Murdoch had apparently suggested and offered here, the hue and cry, especially from Fox News and Republican/Tea Party America, from the Congress to the US Chamber of Commerce to the Heritage Foundation, would be deafening and not be subdued until there was a congressional investigation, and the resignations were in hand of the editor and publisher of the network or newspaper. Or until there had been plausible and convincing evidence that the most important elements of the story were false. And, of course, the story would continue day after day on page one and remain near the top of the evening news for weeks, until every ounce of (justifiable) piety about freedom of the press and unfettered presidential elections had been exhausted.

The tape of Petraeus and McFarland's conversation is an amazing document, a testament to the willingness of Murdoch and the wily genius he hired to create Fox News to run roughshod over the American civic and political landscape without regard to even the traditional niceties or pretenses of journalistic independence and honesty. Like the revelations of the hacking scandal, which established beyond any doubt Murdoch's ability to capture and corrupt the three essential elements of the British civic compact – the press, politicians and police – the Ailes/Petraeus tape makes clear that Murdoch's goals in America have always been just as ambitious, insidious and nefarious.

The digital recording, and the dead-serious conspiratorial conversation it captures so chillingly in tone and substance ("I'm only reporting this back to Roger. And that's our deal," McFarland assured Petraeus as she unfolded the offer) utterly refutes Ailes' disingenuous dismissal of what he and Murdoch were actually attempting: the buying of the presidency.

"It was more of a joke, a wiseass way I have," Ailes would later claim while nonetheless confirming its meaning. "I thought the Republican field [in the primaries] needed to be shaken up and Petraeus might be a good candidate."

The recording deserves to be heard by any open-minded person trying to fathom its meaning to the fullest.

Murdoch and Ailes have erected an incredibly influential media empire that has unrivaled power in British and American culture: rather than judiciously exercising that power or improving reportorial and journalistic standards with their huge resources, they have, more often than not, recklessly pursued an agenda of sensationalism, manufactured controversy, ideological messianism, and political influence-buying while masquerading as exemplars of a free and responsible press. The tape is powerful evidence of their methodology and reach.

The Murdoch story – his corruption of essential democratic institutions on both sides of the Atlantic – is one of the most important and far-reaching political/cultural stories of the past 30 years, an ongoing tale without equal. Like Richard Nixon and his tapes, much attention has been focused on the necessity of finding the smoking gun to confirm what other evidence had already established beyond a doubt: that the elemental instruments of democracy, ie the presidency in Nixon's case, and the privileges of free press in Murdoch's, were grievously misused and abused for their own ends by those entrusted to use great power for the common good.

In Nixon's case, the system worked. His actions were investigated by Congress, the judicial system held that even the president of the United States was not above the law, and he was forced to resign or face certain impeachment and conviction. American and British democracy has not been so fortunate with Murdoch, whose power and corruption went unchecked for a third of a century.

The most important thing we journalists do is make judgments about what is news. Perhaps no story has eluded us on a daily basis (for lack of trying) for so many years as the story of Murdoch's destructive march across our democratic landscape. Only the Guardian vigorously pursued the leads of the hacking story and methodically stuck with it for months and years, never ignoring the underlying context of how Rupert Murdoch conducted his take-no-prisoners business and journalism without regard for the most elemental standards of fairness, accuracy or balance, or even lawful conduct.

When the Guardian's hacking coverage reached critical mass last year, I quoted a former top Murdoch deputy as follows: "This scandal and all its implications could not have happened anywhere else. Only in Murdoch's orbit. The hacking at News of the World was done on an industrial scale. More than anyone, Murdoch invented and established this culture in the newsroom, where you do whatever it takes to get the story, take no prisoners, destroy the competition, and the end will justify the means."

The tape that Bob Woodward obtained, and which the Washington Post ran in the style section, should be the denouement of the Murdoch story on both sides of the Atlantic, making clear that no institution, not even the presidency of the United States, was beyond the object of his subversion. If Murdoch had bankrolled a successful Petraeus presidential campaign and – as his emissary McFarland promised – "the rest of us [at Fox] are going to be your in-house" – Murdoch arguably might have sewn up the institutions of American democracy even more securely than his British tailoring.

Happily, Petraeus was not hungering for the presidency at the moment of the messenger's arrival: the general was contented at the idea of being CIA director, which Ailes was urging him to forgo.

"We're all set," said the emissary, referring to Ailes, Murdoch and Fox. "It's never going to happen," Petraeus said. "You know it's never going to happen. It really isn't. … My wife would divorce me."