A grandmother is only the second woman ever to tackle the bastion of male supremacy at the top of the SIPTU pyramid, in the election to fill the £60,000-a-year general vice-president vacancy created on the retirement last November of Mr Jimmy Somers.
Ms Nuala Keher (45), of Galway, joins Ms Carolann Duggan (39), from Waterford, who has fought for a place on the top floor of Liberty Hall in three previous outings.
There are also two male candidates, Mr Jack O'Connor (43), the favourite to win, who is the current secretary of the union's south-eastern region where Ms Duggan is an active shop steward, and Mr Jack Nash (53), secretary of the SIPTU private sector region in Dublin.
The ballot of the union's 200,000 members began yesterday and will end on May 13th.
Ms Keher, who holds a master's degree in industrial sociology, currently heads the National Open Learning Centre at NUI Galway. She is a former factory worker and CIE level-crossing gatekeeper.
She has been a member of the SIPTU national executive council since 1996.
She was joint author with a SIPTU official, Mr Eddie Higgins, of Your Right to Work, a guide to workers' legal rights.
Ms Duggan's track record in radical union politics is widely known, thanks to her ability with media "sound-bites".
She made union history in 1997 when she was the first rank-and-file member - and the first woman - to contest an election for one of the three general officer slots at the top of the SIPTU pyramid.
This was in a head-to-head contest with Mr Jimmy Somers for the job of vice-president last April. Despite Mr Somers's high profile as a senior official of the union, she managed to get 37,940 votes, or 42.3 per cent of the total valid poll.
She did less well in the subsequent general officer elections, achieving 20.5 per cent against the current union president, Mr Des Geraghty and 22.4 per cent against Mr John McDonnell in the contest for the general secretary post.
Mr O'Connor took over responsibility for the south-east region on the retirement of Mr John Dwan in 1997.
A founder member of Labour Left within the Labour Party in the days of Mr Frank Cluskey, he was a branch secretary of the Federated Workers' Union of Ireland by his early 20s.
He has a good track record - with responsibility within the union for a number of national industrial groups in both the public and private sectors including Roadstone, Readymix and the central and regional fisheries boards.
He has represented SIPTU at national and international level including the National Joint Industrial Council for State industrial workers, the agricultural workers' Joint Labour Council, provender milling JLC and the ICTU public services committee.
Mr Nash has also had extensive experience of the public sector. Derry born, he is a former chairman of the Derry Youth and Community Workshops, a local initiative aimed at creating jobs both for the young unemployed and young offenders.
He has played a co-ordinating role in recent negotiations in a number of major public sector companies including CIE, the ESB and Coillte.
He continues to head the union's campaign to retain the Great Southern Hotel group in public ownership.
Throughout his career he has focused on low pay and social welfare issues.
He firmly believes that SIPTU, as Ireland's largest union, should play an active leadership role in local communities.