Reading SDLP policy documents and Mr John Hume's speeches from the 1970s is amazing. Most of the principles and ideas outlined are now part of mainstream politics. The SDLP has won so many ideological arguments in the North.
The Belfast Agreement is littered with Hume-speak. Both the Ulster Unionists and Sinn Fein - to varying degrees - had to make compromises to accept it. The SDLP generally didn't.
The document's central tenets - a power-sharing government, equality of treatment for the two traditions but recognition that the Union will remain as long as a majority in the North desires - have been party policy for nearly three decades.
As the SDLP celebrates on Monday, the success of the peace process is the greatest testimony to its achievements. In his anniversary statement, Mr Hume expresses natural pleasure. "Our pledge to respect diversity, to include rather than reject, to escape the narrow sectarian mindset, has formed the basis of the Good Friday agreement and given society hope for a new and better future.
"I am very proud to lead a party which has achieved so much, has resolutely stood for equality and stridently opposed violence throughout its history." This sense of justification is shared.
Mr Tim Attwood, the SDLP director of development, notes that Sinn Fein has adopted many SDLP policies. "For 30 years we argued for constitutional politics and against the gun. We were vilified by others who have since been won over to our arguments."
The irony is that despite this vindication, the party has never looked more vulnerable. "We shall overcome" is still sung at annual conferences but the feeling is that the voices are increasingly old, tired and out of touch.
A recent internal review found the party is at serious risk from Sinn Fein electorally and needs to change its middle-class, middle-aged image. Sinn Fein might have stolen the SDLP's clothes but many think it's wearing them in an altogether more attractive fashion.
The depth of the crisis was illustrated by the fact that the review considered a name change but settled for updating the party's logo - an uninspiring two triangles.
SDLP leaders were accused of having pursued a peace strategy at the expense of building party organisation. And the party's "pre-eminent position within constitutional politics" had been "eroded to the point where it is a thing of the past".
The review shows the SDLP is "refreshingly honest", says Mr Attwood. "Could you imagine any other party on this island being so up-front? That proves we aren't afraid of the future and will meet its challenges."
The SDLP has an expanding youth wing, he says. In the past it centred around the universities but now it has "roots in the wider community". Women make up 47 per cent of the party's membership and 40 per cent of the executive.
Despite the perception, most SDLP voters are working-class, insists Mr Attwood.
The SDLP insists the Sinn Fein electoral threat is exaggerated. It points out that it received the largest number of votes in its history - 190,731 - in last year's EU election and its 22 per cent vote in the 1998 Assembly elections made it the largest party in the North.
However, these figures don't tell the entire story. The SDLP vote stood at 22 per cent seven years ago. It became the largest party in 1998 due to the collapse of the UUP vote. Within nationalism, it is Sinn Fein which is making the dramatic gains. Its vote has increased from 12 per cent in 1993 to almost 18 per cent in the Assembly poll.
In pre-ceasefire 1994, the SDLP had four Westminster MPs and Sinn Fein none. Today the breakdown is three to two.
The greatest concern for the SDLP is that 60 per cent of Sinn Fein's vote comes from the 18-34 age group. Only four percentage points separated the two parties in 1998. As more young nationalists join the electoral register, the gap could close further. Next year's council elections will be interesting.
While there will always be a core SDLP vote, the party's ability to attract sufficient new support isn't guaranteed. The internal review spoke of winning middle-class Protestant votes from the Alliance Party, which is seen to be in trouble.
Sinn Fein's popularity has been aided by the huge media attention it secured during the peace process while the SDLP waited in the wings. The Provisional IRA ceasefire won the party support among those - particularly women - previously put off by violence.
The whiff of sulphur from the past, combined with Sinn Fein's growing respectability, is a potent combination, the SDLP admits.
"Sinn Fein is seen as more exciting and dynamic," says a former SDLP representative. "The age profile of our leadership needs improving. John Hume, Seamus Mallon, Eddie McGrady, Joe Hendron, Sean Farren - they are all in their 60s. Mark Durkan is the only prominent figure under 50. That vital second tier of leadership, of people in their 40s, is largely missing."
Also, the SDLP can't match the finances of Sinn Fein, which is widely believed to be the wealthiest party on the island.
Mr Attwood finds Sinn Fein's new financial status exasperating. "In the 1980s, we received training and some funding from the National Democratic Institute in the US. Sinn Fein denounced us and said we were effectively taking CIA money.
"Now Sinn Fein raises more money than any other party from corporate America. Gerry Adams has dinner with Donald Trump - hardly known for his anti-capitalist activities.
"The SDLP's US fund-raising benefited everyone. We helped set up the International Fund for Ireland which created 39,000 jobs. Sinn Fein's fund-raising benefits nobody but Sinn Fein. The money goes to the party, not towards creating jobs or community development."
Sinn Fein's success isn't simply down to financial advantage. The party's relationship with grassroots communities is enviable. The SDLP record is weaker with notable exceptions being Mr Martin Morgan in north Belfast and Mr Danny O'Connor in Larne, Co Antrim.
"Sinn Fein doesn't need to carry out internal reviews to try to be relevant," says a former SDLP member. "There was a telling incident in one constituency during the Westminster election. The SDLP candidate canvassed in his suit and tie. The Sinn Fein man walked the streets in his shirt sleeves. He won."
Mr Attwood believes being in government will suit his party most. Sinn Fein "won't be able to maintain its radical image" when unpopular decisions have to be made in its two departments - health and education.
"We look forward to the move away from the Border-dominating debate. We have very good policies on a range of issues. We are not afraid of competition from Sinn Fein.
"We know we must be more accessible and inclusive than before. But we are the party which finds solutions when others whinge. The SDLP is ready to seize the moment."