Shortly after Donald Trump's inauguration in 2017, I had a conversation with a colleague who specialises in international relations.

At the time, he brushed off concerns that Trump's presidency could turn the world upside down. As he reflected, we will still get up in the morning and the world will still be there.

In the following couple of months, there was growing concern about how robust the institutions and mechanics of democracy would prove to be, and whether they would provide a bulwark against President Trump's disregard for process and propriety.

With the dismantling of many government agencies and cuts to the National Institute of Allergy and Infectious Diseases during a pandemic, he's a leader who has steadily unravelled the structures of the country in which his office resides.

But four years later, what is the real legacy of a Trump presidency?

Well, the legacy of his presidency will stay with us indefinitely.

This isn't simply his legacy on climate change, or the appointment of conservative judges to the Supreme Court.

Trump has opened a space for forms of conduct that have shifted the traditional assumptions about the office of the US president and its function as point of union for that country. He has done so through using the office to preserve and increase his power through fostering division and hostility rather than union.

Of course, it is debatable whether the US has ever been a genuinely united country, resting on unresolved violence towards its Indigenous peoples and the persistence of racialised divisions.

But Trump has opened the gates to the possibility of the US president to speak and act in ways that might, in the past, have been considered unthinkable.

Instead of viewing the office of the president as distinct from his former life, Trump has maintained the same approach to his presidency that marked his business ventures.

Instead of seeing the president as having a duty to the nation and its wellbeing, the president has seen his role quite simply as one of a deal maker, in which absolute power over his enemies has been his highest aim.

Using the same techniques that he used in business – divide people against each other, lie when you have to, and attack your opponent whenever you can – creating divisions and hostility has been instrumental to his attainment power.

As he remarked in relation to his dealings with business partners as well as opponents, "I play to people's fantasies". As a president, he has refined the art of playing to the fantasies of America's white working and middle classes, as well as of newly arrived migrants from Cuba and Venezuela, through actions and statements which appeal directly to the far right and to Christian nationalists in the US.

In the White House, he has dispensed with administrative support staff when he perceived them to be a threat and then subsequently attacked them in the media with blistering ferocity.

There has been extensive commentary on Donald Trump's unfitness for office due to his frequent outbursts and seemingly fragile ego.

Although his allies have attacked what they call the 'deep state', relishing his bile directed at 'political elites', the origins of the office of the US president are deeply embedded in liberal political practice and principles.

Early state building in Britain, for example, was characterised by increasing levels of legislation and adjudication along with a desire to impose limits on office as a counterpoint to Britain's monarchical abuse of power.

With more complex forms of government, there was a corresponding need for the codification of the "duties, rights and relationships" of office. In early modernity this entailed more than simple compliance to a rule. It also required the development of a persona of office which would give form to the exercise of responsibility accompanying that office.

Accordingly, determining the sphere (or parameters) of office and the conduct appropriate to each office informed the development of the persona of that office.

In the continual reiteration of duties, those in office were expected to develop competence and expertise and the "qualities and capacities" to advance its office. Particular human virtues were likewise regarded as key elements in the conduct of office, with the result that the persona of office had a moral dimension; the lack thereof would leave office "misleadingly incomplete".

Ensuring that office holders were fit and proper persons to comply with the conceptual persona of their office and to act within the constraints of office was significant – office bearers "knew the burdens of their sphere and understood the consequences of neglect or excess".

Importantly, developing an account of office also provided people with a predictable and reliable sense of place and status in society, and of their roles and duties.

Against this tradition, the last four years mark a period in which the persona of the office of the president in the US has been corroded by Trump's disrespect for the office he holds and the lack of respect he shows for anyone who challenges his hold on power.

In US constitutional theory, the office of the president has 'two bodies': as a physical body, elected by those who support the values and preferences of the candidate, and as an institution.

In the first case, the US presidency has long been associated with a form of charismatic leadership, possessing will and agency to pursue particular "programmatic preferences".

In the second case, the institution of the president comes with "deliberative practices, substantive commitments and institutional constraints" which ideally ensure limits on the 'will of the sitting president'.

Holding these two together in ways that don't diminish either is a delicate task and perhaps not entirely possible.

However, under Trump, the body of the president as institution has been eclipsed by the desires and the preferences of Trump himself and the institutional commitments and practices of the office have been effectively trashed.

Of course, this can change with a change in the president, and we have seen such disregard before.

Trump's legacy is that he has openly flouted his disrespect for his own office as an institution, while encouraging his followers to do the same.

Most disturbingly, he has stoked social division and racialised tensions in ways that directly threaten the security and lives of others – both in community and in office.

Trump's incapacity (and unwillingness) to recognise the difference between himself, as president, and the institution he embodies, goes against a long constitutional history in the US of respect for the office.

A key measure of his legacy will be the extent of the loss of faith in the institution of the president, and the structures supporting it.

In the aftermath of this 2020 election, the erosion of confidence in US institutions in a society which is increasingly divided, will be Trump's legacy.

This article was updated on 10 November 2020.

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