Mr Biden’s domestic agenda has much in common with Sir Keir’s, and much of Labour’s economic strategy has been borrowed from the Democrats. Both men have expensive green industry investment and labour market reform high on their list of priorities.
However, Trump is sceptical of Western aid for Ukraine, while Labour’s John Healey has described the party’s support for Kyiv as “iron clad”.” Sir Keir has said he would eventually like to recognise a Palestinian state, while Trump is even more strongly pro-Israel than Mr Biden.
There would also likely be differences on China, which Mr Trump has long held as America’s natural enemy and promised to impose fresh tariffs, while taking a hawkish approach to imports he says could pose a threat to national security.
“They will find themselves in a dilemma,” said Klaus Larres, a Kissinger China Institute Fellow at the Wilson Center in Washington. They have to appease the United States for obvious reasons, but also don’t want to give up on China. The UK’s economic relations with China are very intense.”
There are also major differences between the two leaders on climate policies. While Trump has pledged to “drill, baby, drill” and reduce US investment in clean energy, Labour has said it will do the opposite.
If Trump wins power again, London and Washington’s positions on a free trade deal will be reversed. While Mr Biden has blocked a deal during his presidency, Trump has suggested he would be open to striking one.
Labour, meanwhile, is more interested in reaching agreement on “sector specific” deals on tech, pharmaceuticals and other key industries, while avoiding rows about imports of American chlorinated chicken and other agrifoods.
The presumptive Republican nominee, who is facing three further criminal trials after his convictions in the Stormy Daniels “hush money” case, is also sceptical of federal prosecutors who dabble in politics – the exact career path taken by Sir Keir.
Closer to home, Sir Keir must find a way of stopping illegal Channel crossings by migrants if he is to have any credibility over border security. He has said he will work with other countries to find a solution, but has already ditched Rishi Sunak’s plans to send asylum seekers to Rwanda, which was popular with right-wing parties on the continent.
France could look very different next week after it goes to the polls for the second round of its parliamentary elections on Sunday. President Macron has already let it be known he is impressed with Mr Starmer, who last year said had the “moral authority” to become prime minister after a bilateral meeting considered a break in protocol for an opposition leader. But Mr Macron might not be calling the shots if Marine Le Pen’s National Rally wins an absolute majority, which would mean 28-year-old Jordan Bardella becoming prime minister. Ms Le Pen has already indicated that she sees Macron’s role as foreign and defence chief largely “honorific,” meaning she intends with Bardella to muscle in. While Macron has deferred to the EU over immigration, she said she would go further in bilateral, rather than EU-wide, cooperation.
“Britain wants to protect its borders and therefore prevent illegal immigrants from entering the UK. They happen to come from France,” she said.
Bardella is in favour of creating a joint task force in the Channel that would “deport migrants directly to their home countries via charters”. That is unlikely to be on Starmer’s agenda.