The Pè a Corsica (For Corsica) slate, an alliance of Gilles Simeoni's autonomist Femu a Corsica (Let's Make Corsica) and Jean-Guy Talamoni's pro-independence Corsica libera (Free Corsica), won 45.36 percent of the votes in Sunday's first round, leaving them almost certain to be able to control the assembly after the second round on 10 December.
Although turnout was low, at 52.17 percent, the nationalists were in ebullient mood as the results came through.
"This is a very strong message to Paris," Simeoni said. "We want peace, we want democracy, we want to construct an emancipated island. It's up to Paris to take steps so that we can work out a political solution together."
In the 2015 elections for the two assemblies that have since been abolished they won 35.34 percent in the second round, a result that was hailed as a breakthrough for them but only allowed them to form minority adminstrations.
The Corsican representatives of parties based in mainland France received small and, in some cases, derisory votes on Sunday, with the runner-up being a Corsican regionalist grouping and the the far-right National Front (FN) unable to stand in the second round.
Apart from Pè a Corsica, the slates that have made it to the second round are:
A Strada di l'avvene (Future Path), right-wing regionalist, with 14.97 percent;
Voir plus grand pour elle (Think Bigger), representing France's mainstream right Republicans, with 12.77 percent;
Andà per dumane (Forward to Tomorrow), representing President Emmanuel Macron's Republic on the Move, with 11.26 percent.
Three slates did not reach the 7.0 percent needed to stand in the second round:
U Rinnovu (The Renewal), hard-line separatist, with 6.69 percent;
L'Avenir, la Corse en commun (The Future, Corsica Together), Communist Party and Corsica Unbowed, 5.68 percent;
Rassemblement pour un Corse républicaine (Rally for a Republican Corsica), National Front, 3.28 percent.
Not like Catalonia
Hailing a result, "beyond our expectations", Talamoni conceded, "We're not in the same situation as Catalonia," noting that the Spanish region was far wealthier.
"But if a majority of Corsicans want [independence], in 10 or 15 years, nobody will be able to oppose it," he told France Inter radio.
With a large proportion of jobs on the island being in the French public sector and the local economy dependent on national financing, the nationalist alliance dropped the demand for complete independence.
It is calling for a plan for "real autonomy" to be drawn up within three years and put into effect within 10.
Its main demands are for the Corsican language to have official status alongside French, a status of resident to protect local people from the effects of property speculation, and amnesty for members of nationalist armed groups in hiding or in prison.
Groups lay down weapons
In 2014 one of the main armed groups, the FLNC, renounced the "armed struggle", bringing an end to years of bombings and attacks on police stations, as well as the occasional assassination, apart from a few isolated attacks that have taken place since.
Since then, the nationalists have fought on the electoral plane, a strategy that has already borne fruit in this year's parliamentary elections, when they won three out of four parliamentary seats on the island, and is now likely to give them control of the assembly when it opens on 2 January 2018.
On the mainland, Republicans MP Eric Ciotti said he was worried by Talamoni's declaration on independence and said the response must be "more France and better France".
Hard-left leader Jean-Luc Mélenchon, whose France Unbowed had refused to back the Communist Party-led slate, hailed the result. "Bravo! Macron severely punished. the FN reduced to ridicule," he said in a tweet, going on to accused the Communists of "identity theft".
10 things you should know about Corsica
- Pre-revolutionary France bought Corsica from the then-independent republic of Genoa in 1767.
- It was the birthplace of Napoleon Bonaparte.
- It has its own language and a mountainous interior where the law has often been difficult to impose.
- The first Corsican nationalist party, the Partitu Corsu d'Azione, was formed in 1923 by Petru Rocca.
- Regionalist and nationalist movements took off in the 1960s and the FLNC was formed in 1976.
- Since then there have been several splits in the nationalist movement and some overlap with apolitical crime.
- The represantative of central government Claude Erignac was assassinated in 1998.
- About a third of Corsica's GDP comes from tourism.
- In 2010 there were 70,000 second homes on the island, seven times more than 40 years before, compared to 125,000 principle residences, although many of the scond homes are owned by islanders.
- In 2015 a mob attacked a Muslim prayer hall in the main city, Ajaccio, an act condemned by nationalist leaders, and in 2016 a fight broke out on a beach allegedly over a woman wearing a burkini.