Donald Trump’s agenda is to turn the clock back in the United States half a century, to a time when elected leaders spoke the language of white supremacy. Like Mr Trump, they did not use dog whistles. Until 1967, 17 states had laws banning interracial marriage. Mississippi did not vote to ratify the 13th amendment of the US constitution, which outlawed slavery, until 1995. Of course, legal segregation is a distant memory today, and race in America is not the chasm it once was. The country has had a black president and immigrants, white and non-white, have become rich and famous. Yet Mr Trump has, in a short space of time, remoulded the Republican party by excluding and gagging anyone who challenges him. This is no longer a question of the Republican leadership’s inability to deal with the president’s racism, but of its complicity in it.

Mr Trump is an heir to the tradition of American failure on race, one which misunderstands or ignores the country’s fundamental premise that people, in the words of Martin Luther King, “not be judged by the colour of their skin but by the content of their character”. In business such racism might be deplored but considered a private affair. However, in office it is an understatement to say that a bigoted, misogynistic narcissist is unfit to be US president. Mr Trump has long thought that only white people can be considered truly citizens and that immigrants are only conditionally American. So it came as no surprise to hear the US president tell four female members of Congress, all of whom are not white, to “go back” to the countries “from which they came”.

This is straight-up racism and resonates with the foundational idea of white nationalism that Mr Trump has long embraced. In deed and act Mr Trump violates the values the US aspires to uphold – equality under the law, religious liberty, equal protection, and protection from persecution – because he does not believe in them. Last weekend he authorised raids without warrants on thousands of families as part of his ongoing attempt to deport 11 million undocumented migrants, many of whom have lived in the country for years. This week he announced plans to end asylum on the US-Mexico border, which lawyers say will be found unlawful by the courts. Mr Trump’s actions are meant to be a constant reminder of who is in charge, and are a snub to the idea in respect of civil rights that all citizens are equal before the law.

In particular, Mr Trump chafes against the idea that the US constitution is colour blind. Last November he threatened to use an executive order to scrap the guarantee of birthright citizenship in the US. In doing so, he was seeking to take a wrecking ball to the US constitution. Its 14th amendment decrees that any person born in the country is a citizen, and that states may not “abridge the privileges or immunities of citizens”, or deprive them of “life, liberty, or property without due process of law”, or deny them the “equal protection of the laws”. His long record of racism leads one to conclude that Mr Trump thinks such safeguards in the country’s legal rule book should only apply to white people. White Christians are no longer the majority in America, but they’re still driving election results.

Whether or not Mr Trump can actually entrench their rule is not the point. His racism has two purposes: one is to distract voters from his real intent; the other is to energise his voting base as he heads into the 2020 election. His core vote is hostile to sexual and racial minorities. Mr Trump’s calculation is that his political survival depends on inflaming those antagonisms to get his vote out. But there is evidence that such messages of hate do not resonate with the American public. As Mr Trump explodes rightwards, the public mood appears to have shifted sharply left. He wants his base to burn with anger. Americans hopefully will remain, as the polls indicate, thermostatic: when things get too hot, they’ll turn down the heat.