A former rugby international, gaelic footballer, barrister, golfer and greyhound enthusiast, Mr Spring, 47, nicknamed "Groucho" for his dour demeanour, fuelled rumours by declining to confirm he would lead Labour into the next election.
Two damaging poll defeats accelerated the decision. June's general election saw Labour decimated; its 1992 peak of 33 Dail seats cut to just 17. Voters never forgave the party for a 1992 about-turn, when stinging criticism of Fianna Fail's standards was abruptly replaced by coalition with them.
Last week's presidential race saw Mr Spring's choice, the anti-nuclear campaigner Adi Roche, crushed by Mary McAleese, prompting some to question his judgement.
Another factor was the recent death of Mr Spring's mother, Anna. For 50 years she was so dedicated to her first husband Dan and subsequently to her son's constituents (she was even summoned to deliver babies and lay out corpses) that a colleague observed: "She made sure grass didn't grow in Kerry without Dan Spring knowing about it."
Mr Spring became party leader and a cabinet minister at 32 in 1981 barely 18 months after entering the Dail, modernising policy with a pragmatic social democracy, and purging Militant. Civil servants judged him one of the hardest-working ministers.
In 1993, after the IRA Warrington bomb, Mr Spring urged Irish people to wear white ribbons as a protest against the IRA. Addressing the child victims' parents, he wrote in The Independent, "The real Ireland walks in spirit behind the coffins of your sons."
He also forged a helpful, easy rapport with President Bill Clinton, assisted by one Irish aide's masterly golfing tips. By June, Mr Spring was burned out by relentless globe-trotting, European Union diplomacy in Ireland's 1996 presidency, the Northern Ireland peace process, domestic battles and long trips between Dublin and his Kerry seat. Overseas absences also sparked accusations that Labour was losing touch with worsening domestic crime and heroin problems.
Throughout, Labour strategist Fergus Finlay demanded utmost respect for his leader. Sean Duignan, Taoiseach Albert Reynolds' spokesman, quipped "I kind of like Spring, but he's touchy, and when he's not being touchy Fergus is touchy for him."Reuse content