FACTBOX-What happens next after Ireland's "ballot-box revolution"

The Irish nationalist party Sinn Fein appears to have secured the most votes but not the most seats in a national election on Sunday, which its leader described as a "ballot-box revolution" that deserved to be rewarded with a first ever place in government. The formation of the next government could take weeks or months as the two long-dominant parties, Fianna Fail and Fine Gael, told voters during the campaign that they would not govern with Sinn Fein, a left-wing party that was once the political wing of the Irish Republican Army (IRA) guerrilla movement.

WHO ACTUALLY WON? The last of the seats in Ireland's 160-member parliament may not be filled for days yet. In the last election in 2016, it took six days to decide the final contest in the complex "single transferable vote" system.

With 102 seats filled, Adrian Kavanagh, a politics lecturer at National University Ireland Maynooth who specialises in constituency analysis, forecast that the centre-right Fianna Fail would win 41 seats, with 37 going to Sinn Fein and 36 to Prime Minister Leo Varadkar's Fine Gael. WHAT HAPPENS NEXT?

Once most of the seats are filled, talks on forming a governing alliance will begin among the three main parties and smaller groups including the centre-left Greens, the Social Democrats and Labour. In 2016, it took 10 weeks to form a government. WHAT ARE THE OPTIONS?

Sinn Fein leader Mary Lou McDonald said on Monday that her first priority was to establish whether she could form a left-wing coalition without Fianna Fail or Fine Gael. Analysts say this option is unrealistic, both numerically and politically. Instead, there appear to be three options:

FIANNA FAIL AND SINN FEIN Fianna Fail leader Micheal Martin has declined to repeat earlier firm refusals to consider a coalition with Sinn Fein, saying only that there were significant incompatibilities in policy. To reach a majority, such a coalition may need a third partner, as well as the approval of a sceptical Fianna Fail rank and file.

Fine Gael has repeated its pledge not to go into coalition with Sinn Fein, citing its IRA past and differing economic policies. FINE GAEL AND FIANNA FAIL

Fianna Fail and Fine Gael have alternated in power since the foundation of the state in 1922, but have never formed a coalition together. Fine Gael offered to do so after the last election but Fianna Fail declined, instead helping to keep Varadkar's minority government on power by supporting it on major issues from the opposition benches. This time, they might also need the support of other parties. Fianna Fail insisted before the election that it would not strike such a coalition, as it would leave Sinn Fein as by far the biggest opposition party, to the possible detriment of one or both governing parties.

ANOTHER MINORITY GOVERNMENT Fianna Fail could try to lead a mirror image of Varadkar's minority government, relying on Fine Gael for case-by-case support, although Fine Gael deputy leader Simon Coveney said the option appeared unlikely this time.