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 abolish 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.