DUBLIN (Reuters) - If Irish nationalists Sinn Fein turn their national opinion poll lead into a historic election breakthrough on Saturday, it will be healthcare and housing not their signature demand for a United Ireland that will have put them on the brink of power.

Just two years after the retirement of long-time party leader Gerry Adams - seen by many as the face of a bloody Irish Republican Army war against British rule - the left-wing party has become a contender for government for the first time.

Opinion polls on Monday showed the party in front of the country’s center-right duopoly of Fine Gael and Fianna Fail - which have taken turns in power for a century - in a political earthquake for the country of 4.8 million.

While Sinn Fein likely has too few candidates to lead the next administration - a misstep caused by a sudden surge in support - it wants to form part of the next coalition.

Under new leader Mary-Lou McDonald, a 50-year-old Dubliner with no link to the Northern Ireland conflict that ended in 1998, the party has focused on inequality created by a five-year economic boom to win voters who shunned the party in the past.

“This is a different type of election. I’m struck by the extent to which people are saying openly that they want change,” McDonald told Reuters as she canvassed voters in the capital.

“I think the penny has perhaps dropped that, after almost a century, there is life and politics and government beyond Fine Gael and Fianna Fáil.”

Slideshow ( 3 images )

“FEELING FOR CHANGE”

Election leaflets mention the party’s historic goal of reunifying the British region of Northern Ireland with the Republic of Ireland, but below promises on housing, childcare and insurance costs.

On the campaign trail the message is resonating with workers who say their lives are not improving as the economy grows, particularly on the defining campaign issue of the cost and availability of housing.

Sarah Melinn, a 43-year-old credit controller from the west Dublin suburban town of Clondalkin, said she is likely to vote for Sinn Fein for the first time.

“The bottom line with Sinn Fein for a lot of people is ‘IRA, not voting for them,” she said.

“But in the past year I have become a bit more open minded and I am trying to get that out of the way and listen to their political views rather than the past.”

Slideshow ( 3 images )

In Northern Ireland, Sinn Fein shares power with the pro-British DUP as part of the 1998 settlement that ended three decades of conflict over the province.

It has never governed in Ireland, where Adams established it as the third largest party following a devastating property crash a decade ago, securing 14% of votes in the 2016 election won by Fine Gael.

On Monday, Sinn Fein was polling at 25%, ahead of favorites Fianna Fail on 23% and Fine Gael on 20%, in a Ipsos MRBI poll.

But as it is only fielding 42 candidates it will at best secure a quarter of seats in parliament.

And its rivals Fine Gael and Fianna Fail, who have far larger numbers of candidates, have steadfastly refused to govern with Sinn Fein, citing its past as the political wing of the IRA and economic policies.

Yet even if Sinn Fein’s surge does not force one of the bigger parties’ hands, it could establish itself as the undisputed party of opposition, said Gary Murphy, Professor of Politics at Dublin City University.

“I think Sinn Fein’s grand plan is to be in a position to take out Fine Gael or Fianna Fail as the second party of the state,” he said.