A Gerry Adams gaffe on Twitter is one of those things that should be in the training manual for new Sinn Féin TDs.

The Sinn Féin leader’s often strange use of Twitter has long been a source of nervous embarrassment to the party.

Adams himself has jokingly referred to attempts by Sinn Féin to control his tweeting. The reaction from most TDs and party members is to shrug; “That’s Gerry.”

It is harder to shrug off this one, however, and Adams’ rapid u-turn and apology over the course of Monday shows that he knows it.

For Sinn Féin, it is one thing having a controversy about Adams flayed across the front pages in Ireland by those whom the party overtly counts amongst its enemies.

It’s quite another having eyebrows raised in Washington and New York by the use of the N-word in a late night tweet. This is a bigger problem than usual.

In the US political and media atmosphere, so attuned to anything remotely racially charged, it’s a lot more difficult to get away with the “everyone knows Gerry’s not a racist” defence.

As the US wakes up over the next few hours and the story pops up on people’s news alerts, we’ll see if Adams’ second line of defence - “Sure, the Irish are the blacks of Europe” - is any more successful.

But you wouldn’t bet on it. Chances are it might make things worse.

The US remains important for Sinn Féin for reasons of political clout and fundraising, though it’s more important for the Adams generation used to White House receptions and presidential audiences than the younger, often more doctrinally left-wing generation coming into elected office in recent years.

The truth is the party most important project now is the process of transition from one generation of leadership to the next. That is one of the least understood reasons for the strategic decision not to seek to enter government on this occasion.

That transition from the older generation to a younger one is the biggest move for the party since Adams and Martin McGuinness led the party Republican movement slowly and painfully away from armed struggle and towards a normal - or at least more normal - political existence.

The overriding priority for that process is to maintain the unity and coherence of the party’s northern and southern wings. Adams embodies the north-south axis: how to maintain it after him?

He has been president of the party for 33 years. He is 67 now, and occasionally tired. He complains about his back.

He had a poor general election campaign, appearing at sea on economic policy on a number of occasions. True, people have been predicting the end of his leadership for years. They will eventually be proved right.

But not yet. The successful completion of that transition to the next generation is what will finally allow Adams to retire - not an ill-advised tweet, however embarrassing.

Knowing this, Sinn Fein will grin and bear the current controversy with the usual mixture of ruefulness and defiance. Again.