As Gerry Adams well knows, the price of political longevity is that the past is never just the past.

Previous deeds and misdeeds bleed into the present. Ever the strategist, he could see the party he has steered for so long is set for another period of growth but that he, himself, risked slowing that effort.

So after a staggering 35 years as Sinn Féin President, he has now handed over to Mary Lou McDonald. (Her appointment will be ratified at a special ard fheis on 10 February).

Given the premium the republican movement attaches to loyalty and internal cohesion, this has turned into a velvet transition, with McDonald positioned as the safe money bet for several years.

Her inheritance is propitious.

Aside from its growing electoral support – third placed in the Dail – the party’s overall goal – Irish reunification – inches ever closer to reality.

A recent LucidTalk poll asked a cross-section of 18-44 year olds in Northern Ireland whether they wanted to ‘leave’ and become part of a single Irish state or ‘remain’ in the UK. Fifty-six per cent wanted to live in a united Ireland and just 34 per cent opted for the status quo.

In her short acceptance speech, McDonald laid particular emphasis on reaching out to Unionism:

“Uniting this island is the best outcome for all our citizens and it is now our task to convince our unionist friends and neighbours of that and to encourage them to help us build a new Ireland,” she said.

From Gerry Adams, such sentiments would elicit unionist guffaws. Coming from McDonald, a likeable and straight-talking political character, they might just receive a second hearing.

After all, it’s impossible to embroil McDonald in the republican movement’s past.

At a stroke, the party leadership’s historical account is wiped clean. She is, in the parlance, a ‘clean skin.’ A middle class Dubliner who was previously active in Fianna Fáil and, at 48, part of an emerging post-troubles political generation.

Speaking of the southern Irish parties, they dread what comes next.

Warm, witty and combative, the dull grey suits of Irish politics have never worked out how to handle McDonald. The previous Taoiseach, Enda Kenney, used to sit scowling at her in the Dáil as she upbraided him for his various failings like a big sister bossing a moody sibling.

Sinn Fein 2.0 is a frightening prospect for the insular and male-dominated world of Leinster House. A recent poll, found 21 per cent of southern Irish voters would be more likely to back Sinn Féin under a new leader. Even winning a fraction of this latent support would transform politics in Ireland, putting Sinn Féin in a commanding position in both jurisdictions.

So Gerry Adams’ timing is impeccable. Succession planning is something most political leaders are loath to spend much time thinking about, caught up, as they inevitably are, in the moment. Yet Adams, unquestionably one of the most important political figures on the island of Ireland for over forty years, has done just that.

In a career full of carefully contrived moves, his timely resignation and smooth succession may turn out to be a masterstroke: propelling Sinn Féin to heights he knew he couldn’t reach.