AS AN EXAMPLE of decent and disinterested politics, there was the case last week of the Irish ambassador. It was a rescue engineered by four Americans who have a bit of influence in Dublin -- Sens. Edward M. Kennedy and Daniel P. Moynihan, House Speaker Thomas O'Neill and Gov. Hugh Carvey of New York. The event wasn't much advertised, and it will do none of these four men any particular good among their constituents. It was merely a matter of principle.

The issue begins with the Irish Republican Army, which has now degenerated into the kind of terrorism that plants bombs in public places in Northern Ireland, mainly killing Irish women and children. The IRA still draws some support from the United States. Who contributes? Some sentimental Americans of Irish extraction who remember the glorius long-ago and studiously avoid the present unsavory reality.

Ireland's ambassador to Washington, Sean Donlon, gives no aid for comfort to the ultranationalists who collect for the IRA or to anyone who has ties with them. The ultranationalists have been complaining about the ambassador.

The prime minister of Ireland, Charles Haughey, opposes the IRA's violence. But he is on the nationalist side of the quarrel between Ireland and Britain. He wants Britain to get out of the six counties of Northern Ireland that it still rules and transfer them to the Irish Republic. Early last week, Mr. Haughey was considering the reassignment of Ambassador Donlon as a gesture to the nationalists and the irredentist spirit that burns among them.

That's the point at which Speaker O'Neill, Sens. Kennedy and Moynihan and Gov. Carey got into it. They sent Dublin a message to the effect that removing the ambassador would be neither wise nor welcome. A day or so later, Mr. Haughey quietly made it clear that he had dropped plans in that direction.

The atmosphere in Northern Ireland is not happy. The present style of government -- direct rule from London, with the army patrolling the streets -- is nobody's idea of a sound and durable one. The British government is now about to try another experiment in local power-sharing between Protestants and Catholics. The outlook is gloomy, and this is a bad moment to fan up national passions. The intervention by the four American politicians was only an effort to keep things from getting worse. But for Northern Ireland, that is no small contribution