Remember how the White House adviser and arch-schemer Karl Rove was dubbed “Bush’s brain”? Stephen Miller fills that role for Donald Trump.

The balding, skinny-tie-wearing Miller, aged just 31, serves as White House senior adviser on policy and has played an outsized role in the Trump administration so far. He was the author of Trump’s dystopian inaugural address, with its dark invocation of “American carnage”, and also wrote the president’s first speech to Congress, with its hyperbolic references to “lawless chaos” and “radical Islamic terrorism”. He was the co-architect, with Steve Bannon, of Executive Order 13679, better known as the “Muslim ban”, and went on cable news to denounce the federal judges who ruled against it, claiming: “The powers of the president to protect our country are very substantial and will not be questioned.”

One former colleague has described Miller as “a true believer in every sense of the word” with “a better understanding of the president’s vision than almost anyone”. Miller, in fact, was one of Trump's early adopters: in 2014, he emailed friends saying: “Trump gets it. I wish he’d run for president.” In January 2016, he quit his job with conservative Senator – now Attorney General – Jeff Sessions and joined the insurgent Trump campaign, soon becoming a a warm-up act for the property tycoon at his frenzied campaign rallies.

Within the White House, where he was once seen only as a Bannon acolyte, the shrewd and ambitious Miller has today positioned himself also as a close ally of Jared and Ivanka.

In recent weeks, he has become the public face of the administration’s hard-line immigration policy, taking to the White House press room podium – after the resignation of the mendacious Sean Spicer as communications director and the sacking of his foul-mouthed replacement, Anthony Scaramucci, ten days later – and loudly clashing with the CNN reporter Jim Acosta over the new plan to give preference to immigrants who speak English.

In the teeming cast of White House grotesques, the dead-eyed Miller – “He looks like the hitchhiker other hitchhikers stay away from,” joked the late-night talk show host Seth Meyers – stands out as a paradoxical figure. Though he is Jewish and was born and raised in liberal Los Angeles County, Miller has the most extensive ties to the white nationalist movement of any White House adviser, Steve Bannon included.

It would not be an exaggeration to call Miller an extremist – and one whose extremism goes back to his teenage years. “He believes multiculturalism is a weakness, that when we celebrate our differences we are ignoring our ‘American culture’,” his former high school classmate Nick Silverman recalled on Facebook in February. “He didn’t like someone from El Salvador celebrating their homeland, or someone from Vietnam bringing in food from their country of origin. He wanted everyone to celebrate one culture. One country.”

Other former classmates told the US Spanish-language news network Univision that Miller “used to make fun of the children of Latino and Asian immigrants who did not speak English well”. One student, Jason Islas, claims that Miller told him they could not be friends because of the former’s “Latino heritage”.

In a high school newspaper column written three months after 9/11 and entitled “A Time to Kill”, Miller also mocked the idea of Islam as “peaceful” or “benign” and demanded a violent response to “millions of radical Muslims”. Later, he worked with David Horowitz – dubbed an “anti-Muslim extremist” by the Southern Poverty Law Center – to organise “Islamofascism Awareness Week” on college campuses.

To recap: for more than a decade, Miller’s biggest obsessions have been race and culture; Mexicans and Muslims. Who does that remind you of? The truth is that his boss – who has retweeted neo-Nazis and received the official endorsement of the Ku Klux Klan – has recruited a motley crew of far-right nativists to serve in his White House. Bannon, the chief strategist, has bragged about how he turned Breitbart News into “the platform for the alt-right”. Sebastian Gorka, who serves as a “deputy assistant” to the president, is alleged to have once been a member of a far-right Hungarian group.

Miller is a former university pal of the white supremacist Richard Spencer, who has called for “peaceful ethnic cleansing”. Spencer referred to himself as a “mentor” to Miller, telling the Daily Beast that he “spent a lot of time with him at Duke [University]… I hope I expanded his thinking.”

Miller was quick to deny any relationship with Spencer. “I completely repudiate his views,” the Trump adviser told Mother Jones last October. But does he really? In his recent clash over immigration with CNN’s Acosta – which has led to reports that he may be promoted to White House communications director – Miller denounced the reporter for his “cosmopolitan bias”. As commentators and historians have since observed, that deeply loaded phrase has both racist and anti-Semitic connotations.

Let’s be clear: the Trump administration’s plans to cut legal immigration in half and prioritise the speaking of English by new applicants have nothing to do with economics or national security and everything to do with Making America White Again. As the academic Carol Anderson observed in the New York Times, the “guiding principle” of his administration “is to turn the politics of white resentment into the policies of white rage”. (The administration’s support for this immigration bill is also a classic example of Trumpian hypocrisy – the president’s grandfather Friedrich Trump arrived in the US from Germany in 1885, unable to speak English, while according to the 1910 census, Miller’s great-grandmother could speak only Yiddish.)

It cannot be pointed out often enough that this is not in any way, shape or form a normal Republican or even conservative administration. Forget the serial dishonesty and astonishing dysfunction. This is a White House that indulges and panders to far-right bigots and nativists in both coded and not-so-coded language; a government of white nationalists, by white nationalists, for white nationalists. The rise and rise of the odious Stephen Miller, from high school provocateur to senior White House adviser – and maybe now even communications director – is worrying proof of that.

Mehdi Hasan is an NS contributing editor. He is based in Washington, DC