Mr Ailes' role was chronicled in the classic book, The Selling of the President. From then on, he was an acknowledged master of that medium.

Driven by small-town values

Mr Ailes came from a blue-collar background – his father was a factory foreman in Ohio. He has described his upbringing as "God, country, family". Those small-town values have always driven his politics. But his genius as a media figure and political consultant was built on something deeper: a psychological insight into middle America's profound resentment of urban liberal elites.

It was a mindset he spotted in Nixon. He also advised two other presidents, including George HW Bush, and figures such as Rudy Giuliani, the former mayor of New York. It was Mr Ailes, not Lee Atwater, who proposed and filmed the infamous Willie Horton advertisements in 1988 that helped destroy Michael Dukakis' presidential chances and elect Bush senior. Much like Nixon's 1968 campaign and Mr Trump's "Make America safe again" theme, the Horton ads played on white fears of black crime.

But it was only with the launch of Fox News, which will celebrate its 20th anniversary in October, that Mr Ailes began altering the contours of the US political landscape.

Some compare Fox's influence to Rush Limbaugh's daily talk radio show, or Matt Drudge's website the Drudge Report. But Fox's ability to dictate mainstream opinion is far greater than that. At $US1 billion in annual profits, Fox News makes more money than all the other cable TV and network news channels combined. No channel can make or break a presidential hopeful like Fox. Candidates launch their bids from Fox studios and earn their keep in between elections as paid Fox contributors. Among others, Newt Gingrich, Mike Huckabee, Rick Santorum, John Kasich and Mr Guiliani have all been employed by Fox.

One exception is Mr Trump, whose love-hate relationship with Fox last year played out through his public duel with Megyn Kelly, its most highly rated anchor, whom Mr Trump described as a "bimbo". Their reconciliation was brokered by Mr Ailes this year but only after Mr Trump had boycotted a Fox-hosted presidential debate.

The New York property magnate is the first big Republican figure to have taken on Mr Ailes and come off evens, if not better. His rise is perhaps the clearest sign that Fox News' political influence might have passed its peak. To be sure, Mr Trump continues to bask in the support of leading Fox anchors, such as Bill O'Reilly and Sean Hannity. But, unlike his predecessors, Mr Trump can always turn to another medium, Twitter, which has been his chief publicity tool since he declared his candidacy.

Doubtless Nixon would have seen Twitter as a gimmick, as did many of Mr Trump's rivals in the Republican primaries. But as Mr Ailes showed, political success requires mastery of the age's leading medium. It is perhaps fitting that television's "evil genius" is stepping aside just as politics moves on to newer technologies.

Financial Times