In spite of the high level of attention that the rest of the world routinely pays to American politics, very few members of the two houses of Congress manage to achieve a global political profile – as distinct from one in their own state or within the Washington Beltway. George Mitchell achieved this rare feat with great distinction as a peacemaker in the Middle East and Northern Ireland; and at the opposite end of the political spectrum, the baleful Jesse Helms was globally notorious for his isolationist hostility towards the United Nations. In a previous generation, William Fulbright was sometimes the conscience of America during the cold and the Vietnam wars.

Senator John McCain, who died at the weekend, was another of these very rare exceptions. It helped McCain’s profile that he was famous for more than half a century. After he was shot down, imprisoned and tortured in Vietnam his body bore the scars, of which he never complained, for the rest of his life. It boosted his celebrity, though not his reputation, that McCain ran for president in 2008, choosing the pre-Trump populist Sarah Palin as his running-mate. The 2008 race was a dark turning point for American politics, and McCain’s campaign was far less impressive than his unsuccessful run for the Republican nomination in 2000, during which he boldly denounced his party’s conservatives as “agents of intolerance”. The senator’s sense of humour – and his ease with the press – were assets too.

But McCain owed his standing more than anything to two things: his often fiercely independent views and his commitment to multilateralism. He was a maverick rather than a moderate. He had many flaws. But he worked with Democrats to try to control the rise of money in US politics. He cast his vote against the Republican obsession with destroying Obamacare. He opposed torture on moral principle. At the same time he was always a warrior politician, a type that has not existed in democratic Europe since Charles de Gaulle. He was always truly engaged with the world beyond America’s shores. It made his the most important American Senate career since Edward Kennedy.

'American original': John McCain praised by political friends and foes Read more

Look through the list of senators that McCain leaves behind and it is hard to see the next big figure, especially in his own Republican party. This is not an accidental dearth. There are fewer independent-minded Republican members of the Senate now than there were in the past. There are many fewer moderate Republicans too. Most Republican senators spend much of their time watching their own backs. As the party at the grassroots swings ever further towards the conservative right, they have lurched rightwards too. McCain’s death may increase this conservative hegemony. Two of Mr Trump’s all-too-few Republican senate critics – Bob Corker of Tennessee and Jeff Flake of Arizona – have also now thrown in their hands.

These tendencies predate the rise of Donald Trump. Mr Trump has accelerated a process that had already begun in the Newt Gingrich era in the 1990s. Under the majority leader Mitch McConnell, the Senate Republicans had already shifted steadily to the right on issues such as taxes, deregulation, climate change, cultural issues and the nomination of judges tasked with the job of nullifying liberal achievements. It is often said that the congressional Republicans have failed to stand up to Mr Trump, but there is a persuasive argument for suggesting that they were simply waiting for a president like the one they now have to come along.