For the best part of a decade the leaders of Sinn Fein were honoured guests at St Patrick's Day festivities in the United States. The highlight was a White House reception and, at the very least, a photo-opportunity with the President. Meetings with prominent Irish-Americans, Senator Edward Kennedy and Congressman Peter King, were established stops on the itinerary.
This year, the White House celebrations will proceed without Sinn Fein. There will be no high-profile meetings on Capitol Hill. Gerry Adams has been comprehensively frozen out. His place will be taken by the fiancée and five sisters of Robert McCartney, the Catholic man stabbed to death six weeks ago in a Belfast bar.
It is tempting to conclude that a single bereaved family campaigning for justice has thus succeeded where years of British diplomacy failed: in convincing influential Irish-Americans that Sinn Fein, as the political arm of Irish republicanism, maintained a relationship with the IRA that was ambiguous, if not complicitous. And there is some truth in such a view.
Americans like their politics personalised. They lionise self-appointed champions of justice who fight against the odds. They like a principled scrap. The story of the McCartney family's defiance in the face of IRA bullying is tailor-made for America. It will certainly have helped to turn the tide.
Yet the truth is more complicated. The peace process itself, and US involvement in it, depended on the acceptance by all sides of the ambiguity in Sinn Fein's position. The hope was that its leaders, Gerry Adams in particular, would be able to deliver first an IRA ceasefire and then IRA disarmament. Seven years after the Good Friday agreement it can be said that they delivered the ceasefire, but that disarmament, even in the carefully circumscribed form defined in the agreement, turned out to be a peace move too far.
When the latest effort to restore a power-sharing government in Northern Ireland failed at the 11th hour, prospects for further progress looked bleak. The epic Christmas bank robbery, quickly blamed on the IRA, communicated three things. It said, first, that the IRA, or at least a part of it, still had the capability to commit massive raids. It said, second, that there was at least a section of the IRA that was not interested in peace on the terms currently on offer and would cheerfully sabotage it. The fact that no one has so far been charged says, third, that the IRA's rule of omerta still pertains.
The killing of Robert McCartney and its aftermath reinforced all these points. Easily dismissed as the unfortunate result of a bar-room brawl, it assumed exceptional significance because the family refused to accept that non-explanation. Their insistence that the culprits be brought to justice exposed the IRA to accusations that it was running a state within a state. The IRA's "offer" to have those responsible killed only underlined its allegiance to an alternative authority. For all the family's campaigning, there have so far been no arrests.
Here are two egregious cases of simple lawlessness - cases that everyone in Britain, in Ireland and in America can readily understand. They need no interpretation and there is no ambiguity. The only question - still unanswered - is how much at least some in the Sinn Fein leadership knew, and when. What is certain is that they were either unwilling to pass on their knowledge or lacked the power. Neither recommends Sinn Fein as a reliable partner - either in a power-sharing Northern Ireland government or in a durable peace.
It is not necessary to agree with Ian Paisley and his Democratic Unionists that Sinn Fein was never to be trusted. There was a real chance for peace - and it is still not lost. The ceasefire holds. What recent events have shown is that, if Sinn Fein is serious about peace, it must sever all links with the IRA and behave like the legitimate political party it claims to be. With Britain, the Irish Republic and its US allies for once united, Sinn Fein's next step should be clear.