First “Lock her up!” and “Build that wall!”, now “Send her back!”. Donald Trump’s record of using such slogans to normalise misogyny and stoke prejudice has become exhaustive, and ever more overtly racist. His Twitter feeds have even recycled content from extreme-right groups that historians of fascism like me consider deeply worrying. Yet this all proves tremulously popular. Academics who study fascism are well placed to see that Trump’s shoot-from-the-hip public persona is a carefully constructed device, designed to consciously and deliberately break liberal taboos, setting an example to others that they can do likewise.

The most recent ratcheting-up of his endorsement of racist language came this week, displaying once again the powerful relationship between the leader who seeks to embody prejudice in the pursuit of power and followers who convey this power on him in their millions. True to form, it started with a tweet. He told four congresswomen of colour to “go home”, fuelling outrage from many who were rightly incensed by this latest attack on decency in public discourse. Then, during a rally in North Carolina a few days later, he focused on one of these congresswomen, Somali-born US citizen Ilhan Omar.

Trump’s charisma is like a Rorschach inkblot test. People can project on to it what they want to see

Trump’s speech claimed Omar had smeared American servicemen involved in the 1993 battle of Mogadishu, downplayed the 9/11 attacks, called for compassion for recruits to Islamic State, laughed about Americans who were fearful of al-Qaida, blamed the US for the crisis in Venezuela, and held hard-working Americans in contempt. His audience, enraged by a description that layered outrage upon outrage, then chanted back, spontaneously, “Send her back! Send her back! Send her back!”

Trump, meanwhile, nodded approvingly, serene and emboldened. It was a moment of true demagoguery, and far more likely to stick in the memory of his supporters than his later efforts to distance himself from the incident.

His language, stoking anger before allowing his audience to discharge their emotions in a release of indignation, liberating them to break taboos for themselves, was potent. It reflected his now well-established affective bond over his supporters. For them, Trump is seen as no ordinary politician. Whereas others are corrupt or get bogged down in procedure and detail, he projects a bigger picture. While others prevaricate and make excuses, he battles established elites and, if you believe the hype, even gets things done.

In other words Trump is a populist, as he claims to be the voice of the long-ignored people. He is also a nativist, as he speaks only for certain sections of American society while assuming others are, somehow, not American. This is a far cry from Republican presidents such as Ronald Reagan, whose final speech in office powerfully articulated the idea that anyone could become American. Trump is also a charismatic leader. His appeal comes from the vision. It is mythic, not rational. While this does not make him a fascist, it certainly makes him a far-right leader.

‘‘Make America Great Again’ evokes this sense of mission, and Trump supplements it with targeted attacks on those deemed enemies of the vision.’ Photograph: Eric Thayer/Reuters

This charismatic quality, which is central for enabling such taboo-breaking, is particularly interesting to consider. Charisma is a much misused and misunderstood concept. For one of the first to describe the phenomenon, Max Weber, it was an important new component to politics in the modern era. Weber proposed the idea that modern political legitimacy was a mixture of traditional, legal-bureaucratic and charismatic styles.

Simply put, monarchies relied on tradition, democracies on legal-bureaucratic systems and modern dictators on charisma. In reality, Weber recognised all leadership was really a mix of these elements, and democracies could certainly develop their own charismatic politicians. Jean-Marie Le Pen, Viktor Orbán and Nigel Farage are some recent examples of far-right charismatic leaders who have connected emotively with their audience.

Moreover, while Weber felt charismatic leaders had exceptional personalities, he also stressed they were not objectively charismatic. Not everyone will fall for their charm. Charisma emerges not just from personal character, but ultimately from a shared belief in a mission held between leader and followers. Without emotive mass support, leaders cannot be charismatic.

This sense of mission has redemptive qualities. It also sees the world in a Manichean us-versus-them manner. Using these mythic tropes, mission allows charismatic leaders to project a greater sense of purpose. “Make America great again” evokes this sense of mission, and Trump supplements this with targeted attacks on those deemed enemies of the vision: the supposed corruption of liberal politicians is summarised as “Lock her up!” The pain and suffering of migrants are denied through “Build that wall!” And now attacks on American citizens who, for some reason, should not be in the country can be voiced through “Send her home!”

Trump’s charisma is like a Rorschach inkblot test. People can project on to it what they want to see. Some will deny he is a racist and simply view him as fighting for their interests. Others are convinced racists and will feel his presence allows them to say things they believe deeply, but are told they cannot say. Moreover, given its emotional resonance, his appeal is not likely to be dented by rational arguments. Outraging people who decry his racism only adds to the attraction, as does condemnation from political elites.

However, Weber argued that charisma was difficult to sustain. The appeal of Trump will ultimately be dimmed by his own failures to achieve his mission, which is ridiculous and unattainable. This will lead his supporters to lose interest, when he can no longer appear as the magician figure they thought he was. We are not at this point yet, though, and it is difficult to known how long his “magic” will last and what further damage will result.

• Paul Jackson is a senior lecturer in history at the University of Northampton and author of Colin Jordan and Britain’s Neo-Nazi Movement: Hitler’s Echo