Ireland's two historic centre-right rivals forged an unlikely coalition with the Green Party on Friday that shuts the resurgent republicans Sinn Fein out of government.
The alliance brings together incumbent Prime Minister Leo Varadkar's Fine Gael with its ancient foe Fianna Fail -- the two stalwarts of Irish politics.
The premiership is to rotate between the two, with Varadkar reportedly agreeing to assume the leadership after Fianna Fail's Micheal Martin.
On Friday night Varadkar said on Twitter he was "clearing out the office" of the prime minister ahead of a special parliamentary sitting on Saturday set to see Martin voted in as Taoiseach, or prime minister.
Under a rota system Varadkar would reportedly return to office in December 2022.
- Outside parties -
The much smaller Greens become kingmakers in a February election that fractured parliament and left Sinn Fein -- historically associated with the paramilitary Irish Republican Army (IRA) -- within touching distance of a role in government.
"There's work to be done, and we're the ones to try and help make it happen," Greens leader Eamon Ryan said after all three backed the coalition in internal votes among its members.
Had the proposed alliance faltered, Ireland risked the prospect of holding an election while the country clawed its way out of its coronavirus lockdown.
Analysts said left-wing Sinn Fein could savour its role as the main opposition party in the middle of a global health and economic crisis.
"The political establishment rallied to keep us out," said leader Mary Lou McDonald.
"Just because the old political establishment has put up some barrier in our way, that's not going to stop us."
"We're going to be the most effective opposition," added deputy leader Michelle O'Neill. "We can make huge strides forward."
- 'United and strong' -
Varadkar's Fine Gael party -- routed to third place with 35 seats -- was the first to back the deal Friday, giving it support from 80 percent of its members.
"Fine Gael is going to enter a third term in government and this new coalition is united and strong, and up to the challenge," Varadkar told reporters.
Fianna Fail, the EU member state's biggest party with 38 seats in the 160 seat chamber, backed the deal with 74 percent approval.
"We have chosen this route, it has many challenges," said Martin.
"But on the other hand it's also a moment of opportunity and a moment of hope for our people."
- Sinn Fein surge -
The Greens secured numerous flagship concessions in the coalition talks, wielding an outsized influence as a 12-seat bloc vital to providing the alliance with a parliamentary majority.
But progressive party members had reason to be cautious of a deal with Ireland's centre-right establishment.
After entering a coalition with Fianna Fail in 2007, the Green Party was wiped out in the ensuing 2011 general election, losing all six of its parliamentary seats.
In a dramatic upheaval of the status quo, February's general election saw republican party Sinn Fein leap to prominence.
The one-time fringe party won the popular vote with 24.5 percent of first preference ballots, becoming the second-largest force in parliament after running on a left-wing platform.
It now expects to become the main opposition party.
That could act as a vital foothold in a push to power in the next election, analysts said.
"Being the lead party of opposition would suit them well, and I don't think they'd be too worried about a second election," University College Cork politics researcher Jonathan Evershed told AFP.
But the pandemic also improved the prospects Fine Gael, which bled seats in February after pinning its election campaign on success in the politically-tense Brexit negotiations.
An Irish Times/Ipsos MRBI poll published last week showed Varadkar enjoying a 75-percent approval rating.
Government Buildings in Dublin where the three Irish parties are set to govern in coalition
Fianna Fail leader Micheal Martin is nowexpected to be voted in as Taoiseach, or prime minister, in a special parliamentary sitting