For more than a quarter of a century, the Irish republican party, Sinn Fein, has had a clear and undisputed leader, Gerry Adams.

To be sure, Adams has had a leadership partner, Martin McGuinness, but fundamentally, it has been understood that Adams received top billing – he was the party president, the thinker, the charismatic speaker, the international media star.

To think Sinn Fein was to think Gerry Adams.

But now, for the first time since Sinn Fein emerged on the world stage, there is a question as to whether Adams, 60, will continue to lead the party he has guided since he was elected president in 1983 and the movement he has molded for four decades.

In retrospect, it probably shouldn't come as such a surprise to hear the "unthinkable" whispered in republican circles.

Twenty-five years is a long time for any political leader to remain in power, and Adams's time at the helm has not been easy, as he first served as the political face of a paramilitary organization while at the same time working behind the scenes to steer his movement away from a reliance on political violence.

That change would be in the wind becomes all the more understandable when one looks at Sinn Fein's inability to expand out of Northern Ireland, where it wields real power, and become a major political force in the Republic of Ireland.

A decade of political frustration in the South came to a head earlier this summer when Sinn Fein lost the single seat it held in the delegation that Ireland sends to the European Parliament. For party vice president Mary Lou McDonald to lose her Dublin seat was nothing less than a political disaster for Sinn Fein and Adams' leadership.

Once the ink was dry on the story of McDonald's defeat, sniping became inevitable and the first major assault came from a surprising quarter, with Toireasa Ferris, one of the party's rising stars in the South and the daughter of longtime republican leader Martin Ferris, suggesting that Sinn Fein "is suffering an identity crisis," and asking: "What are we trying to achieve in the 26 (the Republic of Ireland) and what do we stand for besides a united Ireland?"

Voters in the Republic of Ireland, Ferris said, "unfortunately see us as a Northern-based party, irrelevant to the everyday concerns of people in the 26 counties. Voters are unclear about what we stand for, which is not surprising as I'm sure many of us are starting to wonder about this also. We have been trying to appeal to too broad a spectrum of people and as a result have lost touch with our base."

Ferris, 29, a Kerry county councilor and the former mayor of Kerry, made her comments after waging an unsuccessful bid for a seat in the European Parliament.

While never mentioning Adams by name, Ferris, in a column written for the republican newspaper An Phoblacht, did not mince words, asserting: "our national spokespeople show the party to be out of touch with its base."

Adams, if he was stung by the criticism leveled by Ferris and by others and increasingly applauded in the South, failed to show it.

In fact, in an interview published in the Irish Times, Adams said he was "energized" by the post-EU election upheaval, noting: "There is work to be done and I intend to do it … I have no intention of standing down."

How long Adams continues to serve as the leader of Sinn Fein is hard to predict. Adams has become an international figure capable of generating attention and raising money around the world, and more particularly, the party has no obvious successor waiting in the wings.

In recent months, Adams has launched an Irish unification campaign, which on one level appeals to the hardliners in his party and also represents the natural instinct of a wounded politician turning to the issues that he knows best. A high-comfort-level refuge.

But seen another way, Adams's decision to focus on unification may be making Ferris's point: spotlighting an issue that has emotional appeal in Northern Ireland but less resonance in the South, where voters are concerned about the crumbling economy and about real-life issues like education, health care, and crime.

Whether Gerry Adams can ever be the face of a political party that makes major inroads in the South is very much an open question, but for now, he is the president and leader of Sinn Fein and it will take someone very smart and very tough to wrest that title away.