John Hume's most recent achievement, his greatest to his admirers, was that of assisting republicans to come in from the cold of terrorist action and enter the political system.
The most pressing task for his successor will be to hold the republicans at bay and deny Sinn Fein its aim of displacing the SDLP as the leading voice of northern Irish nationalism. Under John Hume's sponsorship, Sinn Fein not only went into politics but made sweeping gains that surprised everyone.
This year, for the first time, the party won more votes than the SDLP. This worries many observers in Ireland, since the SDLP appears to be an ageing party without the thrust that increasingly assertive nationalists are demanding. At least two of its three Westminster seats look vulnerable: the SDLP's top people are mostly in their 60s while Sinn Fein leaders are mostly in their 40s or early 50s.
Sinn Fein has a lean and hungry look, with energetic leaders in Gerry Adams and Martin McGuinness, plus formidable election workers. It could also win a handful of seats in the Dail in the next general election in the south.
More immediately, the Good Friday Agreement is in difficulties, facing suspension later this week in the absence of progress on decommissioning. Mr Hume thus steps down at a delicate stage of the peace process, though leaving now means that his successor will have time to rebuild the party.
One of the SDLP's problems has been that the IRA and loyalist ceasefires of the 1990s, followed by the 1998 Good Friday Agreement, represented the culmination of Mr Hume's lifetime's work. His part was recognised in his Nobel peace prize.
But since then the perception is that the SDLP has been sidelined. The crucial arms issue seems to involve primarily the republicans, David Trimble's Ulster Unionists and the British and Irish governments.
The sense that the SDLP has lost relevance is a new one in Anglo-Irish affairs, in that for three decades Mr Hume has been at the centre of political debate and innovation, and the architect of important developments. This stretches back to the civil rights movement of the late 1960s, when he emerged in Derry as the most able of a new generation of articulate Catholics demanding their rights in non-violent fashion.
Central to the peace process was his theory, set out in the late 1970s, that it required a role for not just Dublin but also America. He was viewed as a father of the 1985 Anglo-Irish Agreement, under which London and Dublin would jointly manage the issue. In the late 1980s, his controversial contacts with Gerry Adams led directly to the ceasefires.
Northern Irish politics is still buffeted by crises and instability and in some ways the SDLP has yet to adapt – in the past Mr Hume kept up its vote but now a new leader is needed. However, the warmth of yesterday's tributes to John Hume proves that his place is assured in the pantheon of Irish nationalism.Reuse content