Voters are going to the polls in Ireland after a tumultuous general election campaign during which Sinn Féin has surged into contention as a potential party of government.

The republican party hopes a rise in popularity among young and urban voters will translate into enough parliamentary gains to make it a kingmaker or participant in Ireland’s next coalition government.

On Friday Leo Varadkar played down predictions that his time as taoiseach was about to end amid big losses for his ruling Fine Gael party, saying the election was “wide open”. In the event of a rout, he said he would fight to retain leadership of Fine Gael and lead the party in opposition.

Fianna Fáil, the main opposition party, is tipped to emerge as the biggest party, putting its leader, Micheál Martin, in pole position to woo smaller parties to form a parliamentary majority and ruling alliance.

Mary Lou McDonald on the general election campaign trail in central Dublin this week. Photograph: Brian Lawless/PA

Polling stations opened at 7am on Saturday and will close at 10pm, after which media outlets will report an exit poll. Counting is due to begin on Sunday, with full results expected on Monday or Tuesday.

Residents on islands off the coasts of Galway, Mayo and Donegal cast their votes on Friday to ensure their ballots, which will be transported by helicopter and ferry, reach counting centres on time.

Authorities have issued wind and rain warnings as Storm Ciara barrels in from the Atlantic, which could affect turnout. Ireland’s Six Nations rugby showdown with Wales in Dublin could be another distraction.

Varadkar, 41, Ireland’s first gay taoiseach, hoped an economy humming at near full employment and his handling of Brexit would help deliver a third consecutive term for his centre-right party. However, voter anger at homelessness, soaring rents and disintegrating healthcare services has dominated the campaign and fuelled calls for change.

Leo Varadkar is confronted in Ennis, County Clare, on the last day of campaigning on Friday. Photograph: Brian Lawless/PA

Fianna Fáil has also reaped some backlash because it supported Fine Gael’s minority administration in a confidence-and-supply deal, prompting accusations that the two centrist rivals comprised a duopoly.

Under its leader, Mary Lou McDonald, Sinn Féin, once shunned by voters as the IRA’s political wing during the Troubles, has tapped desire for a leftwing alternative that will deliver better healthcare and more affordable housing.

Smaller leftwing parties and independents fear being swamped in a Sinn Féin tide. The public’s focus on bread-and-butter issues rather than the climate crisis frustrated the Greens but the party is still hoping to gain seats and a position in government.

An opinion poll early this week gave Sinn Féin 25% support, nosing ahead of Fianna Fáil and outpacing Fine Gael, which languished in third. During a final canvas in Cabra, her neighbourhood in Dublin, McDonald, 50, urged supporters to back Sinn Féin as a “vehicle for change”.

The party traditionally underperforms in elections when compared with polling predictions. And it fielded just 42 candidates for the 160-seat Dáil Éireann, the lower house of the Irish parliament, so support will not fully translate into seats.

Sinn Féin also may have shed support when a notorious 2007 murder blamed on the IRA returned to haunt it this week, forcing McDonald to revisit the party’s links with the the terrorist group.

Varadkar, speaking during a final canvas in Ennis, County Clare, said political fragmentation could yield “real difficulty” in forming a government, raising the spectre of deadlock and another election. He and Martin have ruled out entering government with Sinn Féin; Martin has also ruled out governing with Fine Gael, narrowing the options for a viable majority.

Varadkar suggested Fianna Fáil may end up forming a “double trouble” pact with Sinn Féin. “The two of them in bed together – that could set us backwards,” he said. “So people have a big decision to make.”