There are two separate elements in the Maíria Cahill affair: the tragic story itself and the political impact it has had in the South of Ireland. The two should not be confused. The first is a complex and still not completely clear account of how a courageous young woman, a member of one of the IRA's "first families", was raped and sexually assaulted over a lengthy period during her teenage years by an older IRA man. She was interrogated by a Provisional IRA "kangaroo court" and forced to confront her assailant. She decided not to press charges against the IRA people she alleged were concerned because of complicated legal barriers that were stacked against her, but did not withdraw them. And then, some years later, she went public about her appalling experience, and how she had told Gerry Adams about it, on a BBC Spotlight television programme.

The second is that this unhappy story has been caught up in the bitter struggle for power between the mainstream parties in the Republic – Fine Gael, Fianna Fáil and Labour – and Sinn Féin. It terrifies them with its apparently unstoppable rise and ability to capitalise on Government blunders such as water charges to build its electoral support.

The problem for Sinn Féin in this affair is twofold. The first is that Gerry Adams, despite being a brilliant politician – his success, with Martin McGuinness, in persuading the militarists of the IRA to end their violence for a largely internal Northern Ireland solution that was essentially on offer a quarter of a century earlier is testament to that – has one major weakness: because of the constant requirement to defend the IRA as noble freedom fighters,whatever evil deeds they have committed, he will continue to get dragged back into the ugly past by bombshells like this.

The other is that Adams’s credibility as a truth-telling political leader is at an all-time low. Nobody except his party followers believes his claim that he was never in the IRA; few believe that he had nothing to do with the abduction and murder of Jean McConville in the face of allegations to the contrary by leading republicans like Brendan Hughes and Dolours Price; and now nobody believes him when he disputes Maíria Cahill’s version of their conversations about her rape or says that he knows nothing about the IRA “expelling” rapists and sex abusers to the Republic.

Telling the truth

Tony Blair’s chief of staff and “front man” in Northern Ireland, Jonathan Powell, tells of a 1999 meeting with Gerry Adams at which Adams said what he liked about Powell was that “you always blush when you lie, Jonathan”. The senior Northern Ireland Office official with Powell retorted, “unlike you, Gerry”.

In Powell’s words, Adams is “a ruthless and focused negotiator who believes absolutely in his cause”. When upholding that cause – and in his mind he is upholding and progressing it all the time – Adams is unshameable.

When faced with what others see as a self-evident truth, he doggedly continues to deny, dissemble and counter-accuse. Fine Gael TD Regina Doherty spoke for many when she told him during Wednesday's Dáil debate that she would "not believe the Lord's Prayer from his mouth".

Of course Adams is not alone among top politicians in this: Charles Haughey, Bertie Ahern, Bill Clinton, Richard Nixon, Vladimir Putin and Silvio Berlusconi are others who spring to mind.

What is different about Adams is that for nearly 40 years – until quite recently – he had the IRA behind him, and that violent past still scares people. Regina Doherty articulated this when she told the Dáil she was too afraid to reveal the names of eight alleged sex abusers expelled to the South by the republican movement, but would give her information to the Garda.

Like most power-wielding military organisations – and in republican areas of the North the IRA was the effective civil power for nearly 30 years – they did some terrible things. Micheál Martin referred to a teenage boy who was raped by a member of the IRA who was using his family’s home as a safe house.

The journalist Mary Holland used to tell of meeting a clearly shaken Adams in his Belfast office after he had just spoken to a mother who was demanding that an IRA man be castrated because he was sexually abusing her small son.

Then there were the everyday killings and violence – and it is salutary to remember that for IRA supporters, and some other people in this state, the rape of a woman was a crime but the murder of a policeman or a British soldier was a blow for freedom.

If anybody wants to be reminded of the viciousness of the mayhem inflicted on people by the Provisional IRA, I recommend Killing Rage by Eamon Collins, successively an IRA intelligence officer, an RUC informant and an IRA murder victim in South Down and South Armagh in the 1980s and 1990s.

But will anything uncovered by the Maíria Cahill case – even the names of multiple sex abusers expelled to the Republic by the IRA – cause significant numbers of southerners to decide not to vote Sinn Féin in forthcoming elections? I doubt it. It was surely no coincidence that the party received its best-ever opinion poll result, beating every other party, a fortnight after the revelations hit the headlines. People in the Republic appear to be able to compartmentalise – or conveniently forget – Sinn Féin’s former connections with a murderously effective guerrilla army in their desire to hit back at an unpopular government.

Common causes

It is perhaps understandable that what matters for most people are the water charges, the property tax and other continuing manifestations of years of austerity imposed on them by the Coalition. It is, after all, part of a European trend that countries with tough EU-imposed austerity programmes turn to protest parties of all stripes. And Sinn Féin is much less left-wing than Syriza in Greece or Podemos in Spain, and much more serious and electable than Beppo Grillo’s populist Five Star Movement in Italy.

Potential Sinn Féin voters in the South and nationalists in the North will feel one thing in common when they look at how the Maíria Cahill affair has been dealt with in recent weeks in the Republic. They will wonder about the sincerity of mainstream political parties and media which normally have little or no interest in what happens north of the Border working themselves into a frenzy about this issue. The latter will say to themselves that in a few weeks Maíria Cahill will be forgotten. And the former will not be impressed by all the moral outrage expressed when it comes to marking their ballot papers in 18 months.

Andy Pollak was the founding director of the Centre for Cross-Border Studies and is a former Irish Times Belfast reporter