Ian Paisley's party, to no one's surprise, brought religion into it, categorising him as "a Catholic Irish- American from the same stable as the Kennedys". The Paisleyites never did warm to him, though they did sit under his chairmanship before flouncing out when Sinn Fein came to the table.
But last week David Trimble was talking cordially about "George" and making it clear he had no objection to his re-appearance on the scene. And so it is that the ex-Senator will next week go to Downing Street to meet Tony Blair and Bertie Ahern to see if he might help them out of the present difficulties.
The events of last Thursday seemed to demonstrate that the Blairite magic which has been so effective in the peace process has vanished. The PM was seen to use every ounce of his political leverage on David Trimble, but all the persuasion and all the pressure were not enough to achieve a breakthrough.
The pyrotechnics of that day have damaged the peace process and called its credibility into question. It caused many to wonder despondently whether it can ever fully work, or whether Northern Ireland is doomed to a return to large-scale violence, or perhaps to a surly limbo between peace and war, lacking the vital underpinning of an agreed political settlement.
In the past few days it has emerged that there is still life in the process and that a holiday and a period of reflection might help pep up flagging political spirits. But although hope is not dead, it is in short supply, and that is where George Mitchell comes in.
From the minute he first became involved in Northern Ireland in early 1995, then in the role of Bill Clinton's economic envoy, his American "can do" manner generated both optimism and interest. His style was not that of brash and impatient hubris. Instead, it was obvious from the word go that this was a mature and seasoned statesman, a major player with abilities far in excess of those normally seen in Northern Ireland. In the years that followed it was often embarrassing to watch the mismatch between his consummate skills and some of Belfast's political pygmies.
Things have not improved in this regard, for it was evident that some crass political misjudgments helped make Thursday's events more harmful than they need have been. The shallowness of the pool of political talent became painfully obvious when two members of the Ulster Unionist executive could not explain the distinction between prior and simultaneous decommissioning.
Having sat for hours listening to such stuff, Mitchell is aware of how wearisome Northern Ireland politics can be. And he will be under no illusions about how difficult the de-commissioning nut will be to crack, for he literally wrote the book, or rather the report on it, back in 1996.
He will also know that in coming back he will face not only the politically uninformed but the politically unreasonable. In his book, Making Peace, Mitchell recalled walking into the conference chamber for his first encounter with the Rev Ian Paisley, who objected to his chairmanship.
He wrote: "There was a noisy commotion. Paisley was standing and saying in a loud voice, `No. No. No. No.' He repeated it over and over again. I was extremely uncomfortable. Although I had read and heard a lot about Paisley and his tactics, this was my first direct exposure to them, and it was shocking. I was accustomed to rough-and-tumble political debate but I'd never experienced anything like this."
It turned out that George Mitchell was not an Irish-American Catholic but a Maronite Christian, though he had Irish connections. His grandparents, who were called Kilroy, emigrated to America from Ireland. Not being able to care for their son, George Mitchell's father, they placed him in a Boston orphanage.
His father wound up in Maine, adopted by a janitor and his Lebanese wife, a woman who could barely read or write in English. From this unpromising start Mitchell has become one of the US's foremost public figures. He was by turns an army intelligence officer, a trial attorney and a federal judge. A liberal Democrat, he spent 14 years as a US senator. He was majority leader in the Senate, where for six consecutive years his peers voted him its most respected member.
He left the Senate unexpectedly in early 1995 and declined a nomination to become a Supreme Court judge. But one night in Clinton's study, following a small dinner party, the President asked him whether he was interested in other roles "or are you just turned off by politics?".
Mitchell's answer, that he was still interested in public service, was to propel him into Northern Ireland. The economic envoy post led on to a more direct and more sensitive role when he was asked to draw up a detailed report on decommissioning.
His conclusion was that to expect decommissioning in advance of political talks, which was the position of John Major's Government, was unrealistic. But he decided it was also unrealistic to think that unionists would go into talks without something to assure them about paramilitary arms. His report suggested that a reasonable compromise would be for negotiations and de-commissioning to take place in parallel. Even before it was published, however, Mitchell was aware the Government would reject it, since Major had told him this at a private meeting in Downing Street.
Rejection led on to the IRA attack on Docklands which plunged the peace process into crisis. But the process moved on, and when negotiations opened in mid-1996 George Mitchell was their chief chairman.
His presence in such a key role was partly due to his judgment and much- admired patience, but also a sign that the US had become a powerful and apparently permanent player in the peace process. At the time this was mightily resented by sections of the Conservative Party, and of the wider establishment.
Today, however, US involvement is acknowledged as a fact of life, and to all appearances a welcome one to Tony Blair. In some ways this is an acceptance of realpolitik, but it is also due to the fact that the nature of the US intervention has changed radically.
Once American and above all Irish-American involvement was viewed as pestilential meddling, with the US seen as a source of IRA guns and money. The State Department and the White House were generally Anglophile, but the Senate and Congress were seen as pro-Irish nationalist and sometimes republican.
All that has changed in recent years. Bill Clinton, once reviled for giving a US visa to Gerry Adams, is now viewed in Belfast as being much more evenhanded, and has been cheered by both Catholics and Protestants on his visits to Northern Ireland. The days are gone when Americans saw it as a simple question; now Clinton calls Trimble probably as often as he calls Adams. George Mitchell is a sign of this new approach, the hours he has spent listening to Belfast politicians serving as a symbol of the new recognition of the complexities of the problem.
Over the years he has come to know all the protagonists well. Gerry Adams he describes as a charismatic leader with "political skill, eloquence in the spoken and written word and above all a relentless determination in the pursuit of his objectives".
He describes a meeting with Trimble in the run-up to the Good Friday Agreement: "He was obviously upset. He began by dropping a document on the table in my office. Since it was more than 60 pages long it made a loud dramatic thud in the gloomy silence. `It's a bad paper. A very bad paper.' It was a short meeting. It wasn't friendly, but Trimble wasn't rude or personally insulting."
Mitchell identified what last week became glaringly obvious and led to Thursday's fiasco: "At the heart of all the problems in Northern Ireland is mistrust. Each disbelieves the other. Each assumes the worst about the other." He will be all too aware that, in the absence of such trust, breaking the decommissioning deadlock will entail an almost superhuman effort.
Yet he carries the memory of how it was done at the time of the Good Friday agreement, and the hope that next time round Trimble might say yes instead of no. It was one of the most emotional moments of Mitch- ell's life, he has said, when he took the call from Trimble and heard him say: "We're ready to do the business."
The recollection of that signal success may help keep Mitchell going in times as gloomy as this. He lived through many dark moments before the Good Friday Agreement was won. His return to Northern Ireland would signal that the world, though mightily exasperated, is not yet ready to give up hope of eventual success.