Joe Biden is not the right man to convince the DUP to back Rishi Sunak’s Brexit deal for Northern Ireland.
The US President is guaranteed a rapturous welcome on a “homecoming” tour of the Republic of Ireland.
But he will get a cooler welcome when he arrives in Belfast on Tuesday evening amid celebrations for the 25th anniversary of the Good Friday Agreement.
Mr Biden, a Catholic who is fiercely proud of his Irish roots, will meet the leaders of Northern Ireland’s major political parties on Wednesday.
He will urge them to return to power-sharing, which the DUP has refused to do after pulling out of Stomont more than a year ago over the Northern Ireland Protocol.
Mr Sunak struck a deal with the EU over the Irish Sea border in February, but DUP leader Sir Jeffrey Donaldson has demanded more changes before he will end the boycott.
Now, Mr Biden will throw his weight behind the building pressure on Sir Jeffrey to restore the devolved institutions created by the Good Friday Agreement.
His task is made more difficult because Mr Biden is a hate figure for some loyalists and unionists.
The president’s threats to Britain during the Protocol row convinced them he was with Brussels and Dublin, and not unionism.
The president, who rarely misses a chance to describe himself as Irish, hasn’t helped matters.
“If you are wearing orange, you are not welcome here,” he joked when welcoming the Irish Taoiseach to the White House in 2015.
He has also blamed “the Brits” for forcing his great-grandfather to flee Ireland for the United States.
Even the world’s most powerful man will struggle to convince Sir Jeffrey to end the boycott, and effectively back the new Brexit deal, before local elections in May.
The DUP fears bleeding support to hardline unionists, who believe the Windsor Framework is cutting Northern Ireland off from the rest of the UK.
Another bloody nose after last May’s Stormont elections – which saw the DUP lose its status as Northern Ireland’s biggest party to Sinn Fein for the first time – could spell the end for his leadership.
Unionism’s psychodrama is exacerbated by the fresh impetus behind Irish reunification since Brexit and last year’s census showing Catholics outnumber Protestants in Northern Ireland for the first time in its 100-year history.
Sir Jeffrey is struggling to contain divides between his Westminster MPs, who favour prolonging the boycott, and his MLAs, who prefer a return to Stormont after a year’s deadlock that delayed action on the NHS and cost of living crisis.
In the anniversary week of the Good Friday Agreement, he will remember the fate of the Ulster Unionist Party, which was once the largest unionist party in Northern Ireland.
The UUP backed the peace deal but was hollowed out by a string of defections to the DUP, including Sir Jeffrey himself, and has since slid into irrelevance.
The DUP will lose support if it accepts the Windsor Framework, but no Brexit deal will satisfy the most hardline unionists.
Now Sir Jeffrey faces a similar choice to his old UUP boss David Trimble. Should he be the statesman and compromise, but lose his loyalist base?
Even if, as some suspect, Sir Jeffrey is minded to ultimately accept the deal, he can’t be seen to do it under pressure from a US president whose colours are nailed so firmly to Ireland’s mast.