The day after U.S. President Donald Trump learned that a gossipy White House tell-all included quotes that his son was “treasonous” and his daughter “dumb as a brick," Trump's mysterious billionaire backers Robert and Rebekah Mercer did a very rare thing and publicly fired back.

Rebekah Mercer issued a statement about Trump’s former strategist and Mercer family friend Steve Bannon — the source of the offending comments — that sawed him off like a gangrenous limb.

“My family and I have not communicated with Steve Bannon in many months, and have provided no financial support to his political agenda, nor do we support his recent actions and statements,” it said.

Five days later, Bannon was fired from his perch at the top of Breitbart News, where Rebekah Mercer is a shareholder.

Most of the commentary that followed focused on whether the Bannon-Trump collaboration was well and truly over. Less attention was given to the news that the Mercers’ estrangement from Bannon had actually begun months earlier, and that this might be the more consequential breakup.

It seems that a year after Trump's election, their association with Bannon had become an embarrassment for them.

Bannon’s relationship with Robert Mercer is cited in a remarkable lawsuit brought by David Magerman, a former employee of Mercer’s hedge fund, Renaissance Technologies. On its surface, the lawsuit is a wrongful dismissal complaint against Mercer. But at its heart, it is an indictment of Mercer’s character and reputation that draws together his political views, his connections to Bannon and Trump and racist comments Mercer allegedly made to Magerman directly.

'If the world knew what [Mercer] was trying to do, they wouldn't stand for it.'

“I have a lot of respect for Bob Mercer. I think he’s a very intelligent person, a very thoughtful person,” Magerman told me recently. But he quickly added, “If the world knew what he was trying to do, they wouldn’t stand for it.”

Seen from a distance, Mercer can appear like a Bond movie villain. A computer scientist-turned hedge fund billionaire, he is reclusive and taciturn. He does not do interviews. He stays out of sight sailing the world in his luxurious, high-tech super yacht, Sea Owl, or holed up in his Long Island estate, Owl’s Nest, while plotting the political transformation of America.

But when he backed Trump’s presidential campaign in 2016 and helped install Bannon to run it, people began asking more seriously, “Who is this man?”

Mercer barely talks to anyone. Trump once joked at a party that the longest conversation he’s ever had with “Bob” was just “two words.” That’s an anecdote from Jane Mayer’s 2017 profile of Mercer in The New Yorker, which, like most of what’s been written about him, was based on evidence from people such as Magerman.

Magerman is a multi-millionaire — the lower nine-figure range, he said — who, like many employees at Renaissance Technologies, became rich through his relationship with Mercer. Unlike most of them, Magerman is not afraid to be publicly critical of how Mercer has used his money in politics.

“People weren’t aware of what was going on [in 2016]. It looked like some eccentric billionaire was giving money to political causes the way people normally do,” Magerman said. “I knew that he was actually trying to do something different than that.”

Mercer’s fortune and Bannon’s media instincts combined with a shared ideology to produce the anti-liberal, anti-Clinton ecosystem that includes Breitbart, the conservative non-profit Citizens United, the book Clinton Cash and much more. Together, they oversaw the data analysis company Cambridge Analytica, whose impact on the UK’s Brexit referendum and the 2016 U.S. election remain troublesomely murky.

For a long time, even Magerman didn’t know about Mercer’s political interests or his ultra-libertarian, minimalist-government goals.

“When I read all that, I felt not only did I have to do something,” Magerman said, “but I’d been negligent in not doing something earlier.”