A young European leader flies to Washington on an official visit. He is a modernising charmer from the progressive wing of politics, articulate and comfortable with the media. He arrives to meet an American president whose politics are emphatically not his, and whose election has dismayed US liberals, disrupted the transatlantic alliance and alienated European opinion. The new US president is an American exceptionalist. He is no respecter of human rights and international institutions. But the European leader has decided to hug him close in the hope of influencing his decisions. Washington rolls out the red carpet. It is captivated by the visitor’s eloquence and charisma, such contrasts to their own leader’s bombast. Improbably, the two men find themselves starting to make big plans together.

For anyone whose memory goes back to the run-up to the Iraq war, this is a sobering vision. When Tony Blair first visited George W Bush in 2001, he began a process that would end, among other things, in the wreck of his own reputation, the collapse of his party’s electoral ascendancy and the undermining of his country’s moral and international standing, all of which continue in some degree to this day. Whether Emmanuel Macron, who arrived in Washington on Monday for a two-day state visit to Donald Trump, will give way to a Blair-like hubris in his dealings with the White House is too early to say. There are sound, serious reasons for thinking history will not repeat itself. But the risk is undoubtedly there.

Mr Macron’s courting of Mr Trump is not an end in itself, as Britain’s often abject obsession with the so-called special relationship can be. It forms part of a coherent, but controversial, attempt to relaunch France, at home and abroad, as what he calls a startup nation. Mr Macron wants France to reassert itself on the international stage as a necessary ally, claim global leadership on issues like climate change, and renew its military role while leveraging France’s huge soft-power assets. This will come to little if he fails to win his current confrontations with French unions. But American isolationism, German caution, EU divisions and a distracted Britain have created large openings for a determined leader who has often made his own luck.

French public opinion likes its leaders to play a global role. But it is as hostile to Mr Trump as any in Europe. Mr Macron needs something more than White House and Capitol Hill plaudits this week if his pragmatic approach is to convince at home. Thus far, his record is not impressive. Mr Macron has not hidden his disagreements with Mr Trump. He has pressed the US president to reverse his abandonment of the Paris climate accord, to keep the US engaged in Syria to constrain the Assad regime, to hold off on his wish to pull out of the Iran nuclear accord and to pull back from his planned tariffs on EU goods.

None of these has succeeded. If he can shift Mr Trump on any of them, Iran in particular, it would be a surprise and a coup. The epiphenomena of the visit – the handshakes, tweets, pouts, talk of bromance and the fact it will overshadow Angela Merkel’s visit at the end of the week – will inevitably dominate this week’s headlines. That also happened when Mr Blair went to Washington in 2001 for a meeting that seemed at the time to be merely about toothpaste and sweaters. But beyond the symbolism of Monday’s dinner at George Washington’s home, where the key to the Bastille, a gift to the first president from the Marquis de Lafayette, hangs in the entrance hall, the substance of the Macron visit needs to be real. If that happens, the rest of Europe would owe a debt to the French leader.