As the 2024 US presidential primary campaign season begins, the most likely final contest is a rematch between President Joe Biden and Donald Trump. Judging by the electoral map in 2020, Biden would be well-placed to win. But American politics is unpredictable, and any number of health, legal or economic surprises could change the outlook. Hence, many foreign friends have been asking me what would happen to US foreign policy if Trump were to return to the White House.

The question is complicated by the fact that Trump himself is unpredictable. The presidency was his first political office and his background translated into a highly unconventional political style. His success as a reality-television star meant that he was always focused on keeping the camera’s attention – often with statements that were more outrageous than true, and by breaking conventional norms of behaviour.

Trump also intuited that he could mobilise discontent, by decrying the uneven economic effects of global trade and stoking resentment over immigration and cultural change, particularly among older white males without a college education. With a constant drip of populist, protectionist and nationalistic statements, he earned himself equally constant media coverage.