When the 1974 impeachment hearings turned south for former US president Richard Nixon, his aides blamed the media.

Frustrated with the dire relationship the president had with the television news, they drafted a 15-page memo titled: "A Plan for Putting the GOP [Republican party] on TV News."

"People are lazy," they wrote. "With television, you just sit — watch — listen. The thinking is done for you."

The plan didn't come to fruition before Mr Nixon resigned.

But the handwritten notes scrawled on the plan ("basically a very good idea. It should be expanded") belonged Nixon aide Roger Ailes — the man who proved instrumental to Rupert Murdoch's decision to launch Fox News two decades later.

Today, the right-leaning, round-the-clock network has covered Donald Trump's impeachment hearings in a way not dissimilar to the plan Ailes himself helped shape.

But it's also done something Mr Nixon's aides might not have expected — experts say the President needs Fox News more than Fox News needs the President.

In today's impeachment battle, the stakes are higher than ever

The difference in how America's news networks framed the first day of the public Trump impeachment hearings was stark:

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Buzzfeed's Ryan Broderick explained how the Republican strategy to defend Mr Trump at the hearings worked:

"Each round of GOP questioning is not meant to interrogate the witnesses, which today included (Gordon) Sondland, but instead to create moments that can be flipped into Fox News segments, shared as bite-size Facebook posts, or dropped into 4chan threads."

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After more than two weeks of hearings that included "bombshell" revelations, American voters remain almost evenly split — along party lines — on the question of impeaching Mr Trump, according to FiveThirtyEight.

At a time when Fox News' public defence of Mr Trump will be crucial in the battle to convince voters that impeachment is unfair, the network's ratings have never looked more dominant.

Fox is king of US cable news

Every year, Fox News generates more than $US2.7 billion ($4 billion) in revenue and two million primetime viewers — more than the other news networks combined.

A study in 2014 found that 84 per cent of consistently conservative Americans said they got their news primarily from Fox.

The network has been called everything from America's "State TV" to "the President's personal propaganda machine".

The Fox News offices in New York City. ( Reuters: Andrew Kelly )

Its influence is so palpable that researchers coined the term "Fox News Effect" to describe how the introduction of Fox to a new market pushed more voters in that market to a Republican political stance.

Matt Gertz, the director of the liberal non-profit Media Matters, says Fox has essentially rewritten the script for what TV news could be, becoming the communications arm of the Republican party. Mr Gertz has studied Fox for over 12 years.

"It's an organ that speaks directly to the Republican base in a way that other outlets don't have the resources to do," he said.

Given Fox's power among voters, it's no surprise that politicians of all stripes flock to Mr Murdoch's office. Mr Trump joined them in 2015.

"I think they've had to play a little bit different a game in terms of understanding their audience," explained Kelley Vlahos, a former Fox News staffer.

"There has always been a close relationship between Republican candidates, Republican officials, the Republican Party and Fox News. [...]

"It's natural that Fox has taken up the mantle of trying to point out some of the more positive things he's doing or, more typically, combating the opposition."

Fox News initially ignored Trump the candidate

Privately, Mr Murdoch discussed Mr Trump's appeal as an outside character who could drive ratings, but he did not think of him as a credible candidate or agree with his political stances, according to Michael Wolff's 2018 book Fire and Fury.

The lack of coverage put the pugnacious Mr Trump in his favourite place: a fight.

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As the campaign continued in earnest, Mr Trump turned to social media and a crop of new right-wing outlets like Breitbart News to get the coverage he lacked, often criticising Fox News along the way. Attention followed, and Mr Trump leveraged that attention to cultivate a diehard following.

When Mr Trump boycotted the second primary debate over a dispute with Fox's then-host, Megyn Kelly, it saw only half the audience of the first. For network executives, the message was clear: If the fans had to choose between Fox and Mr Trump, Fox would have suffered for it.

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In the following months, Fox News gave the candidate more and more serious coverage.

Just a few months before election day, several Fox News opinion hosts declared their wholehearted support for Mr Trump.

Fox News changed when Trump won, and so did its staff

Mr Murdoch fired a host with unpredictable opinions and replaced her with Tucker Carlson, a right-wing writer who's been criticized for condoning white nationalists.

Then, when Megyn Kelly left the network (blaming, in part, her feud with the President), the network gave her primetime spot to Sean Hannity, an opinion host who helped promote Mr Trump's birtherism conspiracy theory.

Mr Hannity reportedly talks on the phone with Mr Trump most nights and has scored more than 13 exclusive interviews with the President since he took office, more than double the number of any other network.

It was Mr Hannity who urged the President to install former Fox co-president Bill Shine as deputy chief of staff. Mr Shine was ousted from Fox over accusations that he covered up rampant sexual harassment at the network.

Mr Shine resigned in March to take a position on Mr Trump's campaign team. He's still being paid more than $US7 million ($10 million) a year by Fox as part of his severance package.

Mr Trump has also employed foreign policy experts and communications staff who also once served as Fox commentators. Ben Carson, John Bolton, KT McFarland, Anthony Scaramucci and Heather Nauert are just a few names on the list.

The staff exchange flows both ways.

Former press secretary Sarah Sanders joined Fox News as a contributor. Former White House communications director Hope Hicks serves as Fox's chief communications officer, and former deputy press secretary Raj Shah is a senior vice-president.

Fox listens to Trump. Trump listens to Fox

In 2017, the network retired its old slogan "Fair and Balanced" for "Most Watched and Most Trusted."

By November 2018, Sean Hannity and another Fox News host were openly campaigning for Mr Trump. They joined him on stage during a rally, pointed to the reporters at the back of the room and yelled, "fake news."

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In December 2018, Mr Trump's aides said he listened to Fox guests and hosts over his staff. For days, Fox news shamed the President for intending to compromise with Democrats over border wall funding to prevent a costly government shutdown.

In the end, he chose not to compromise, and the 35-day shutdown was the longest on record.

In February 2019, Politico reported that Mr Trump had given 55 television interviews while in office. Forty-five of those were with Fox News.

Media Matters, the liberal non-profit that tracks Fox's influence, has noted over 200 instances of Mr Trump tweeting favourably about Fox News to his 58 million followers since August 2018.

Axios reported that Mr Trump spends over two hours of "executive time" watching Fox News every morning.

"I think it's pretty clear that the network is playing an unprecedented role in shaping the President's worldview," Mr Gertz of Media Matters said.

"It's very concerning for a whole host of different reasons. [...] The information that is highly useful to create a right-wing television show is not the information that we necessarily need to make good decisions as President of the United States."

Hypothetically, what if that support wasn't there?

There have been times that Mr Trump has publicly criticized Fox News for not doing enough to portray him favourably.

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But it's hard to imagine Fox News's influence would dwindle if the network lost the President's loyalty, according to Erik Wemple, media critic for the Washington Post.

"[Mr] Trump could denounce Fox News up and down, but those viewers, I think, would still tune in," he said.

"Fox News has tapped into something in this country that is very real and very profitable. And there's no-one else really out there that is that is challenging them."

That hasn't stopped Mr Trump from trying — he has increasingly referenced One America News Network, a niche channel that's more reliably favourable to the President than Fox, but has ratings lower than the tennis channel.

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The President "would love to be able to play kingmaker in cable news," Mr Wemple said. "But still these news habits are pretty well ingrained."

The Atlantic reports that inside Fox News, those critical words from the President in August barely merited discussion, let alone concern that ratings could drop.

For Mr Trump, the stakes are higher. He'll soon devote all his energies to his re-election campaign. And he'll be hoping to court the votes of Americans watching Fox News.

In the end, Fox News has power beyond the President

Ms Vlahos says that working in conservative media made her see that Fox is more a symptom of today's media illnesses than a driver of it.

She notes that since the age of the internet, raw, incendiary voices have gotten a bigger share of the spotlight.

"Opinion writing is muddying the waters of traditional reporting," she said. "The newspapers and television networks have been gobbled up by conglomerates. Their main goal — their main motivation — is to make money and drive ratings up.

"I think, after all these years, people have moved on. I think they realize it for what it is. And this is entertainment, as well as news, and maybe sometimes more entertainment than news."

Others suggest that Fox is doing real damage to America's collective understanding of truth.

A study by Harvard Law School concluded that lies from far-right extremist websites travelled easily to outlets like Fox News and only occasionally got corrected.

Meanwhile, Fox borrows phrases from Mr Trump in calling other networks "the enemy of the people" and "fake news."

The network labelled Robert Mueller's Special Counsel investigation a "deep state coup", Democrats "America haters" and illegal immigrants "invaders" — a term used by white nationalists and the perpetrators of fatal mass shootings in recent months.

More recently, the impeachment proceedings have been called a "Soviet-style" measure by Fox's primetime hosts and the Republican party.

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Fox News's influence is so strong and omnipresent that Mr Wemple cannot imagine the network ever failing.

"People say, 'oh it's never going to last. It's going to fade away because the audience is going to get too old.'

"Well, the audience has aged. And you know what? The United States has produced new audiences."

In other words, Fox News will still be here in 2021 — regardless of who's sitting in the Oval Office.