When Donald Trump lands in Dublin on Saturday for his first presidential visit to the Irish capital, there will be little of the sense of occasion that has greeted some of his predecessors. The US president will be swiftly ferried from the airport to the Phoenix Park for a brief round of engagements.As always with Trump, an unpredictable outburst cannot be discounted. But Micheál Martin, who will greet him at Farmleigh, has already shown he can ably navigate these encounters. For Catherine Connolly, Trump’s courtesy call to Áras an Uachtaráin may prove a sterner test, balancing diplomatic niceties with her strong views on his policies.Following a brief press conference at the US ambassador’s residence in Deerfield, Trump will depart for his golf course in Doonbeg and the Irish Open, plainly the primary reason for the trip.The weekend’s events are the latest manifestation of how Trump, more than any previous holder of the office, has blurred the line between the presidency and his own business interests. Well-informed analysts have already concluded that this is the most corrupt administration in American history, with the Trump family amassing vast sums from dubious cryptocurrency schemes and opaque foreign ventures.That is not all. In the 20 months since his inauguration, he has turned the justice department into an instrument of personal vengeance, sent armed troops and masked immigration agents onto the streets of American cities over local objections, and mounted an unprecedented assault on universities, law firms and the press.Overseas, he has undermined alliances with America’s democratic partners through threats and trade wars while fawning over its authoritarian adversaries. His military carried out the brutal but successful removal of Venezuela’s head of state, emboldening him to attempt the same in Iran, with the predictably disastrous result of a grinding regional war. That, together with his indiscriminate use of tariffs, has done lasting economic damage at home and abroad.Trump is a bully and a braggart, a self-confessed sexual predator and a purveyor of racial slurs. He is probably the worst president Americans have ever elected. Most people would not welcome such a man into their home, and the majority of Irish people will not welcome this visit.Heads of state and political leaders must make a different calculation. Whatever the qualities of the man, the office deserves respect as part of the deep bonds between Ireland and the US. Trump’s term will end, and it is to be hoped his country finds a way to erase the stain he leaves behind. The US remains a great nation, and its many friends, in Ireland and beyond, can only wish it a swift return to its better self.