The poll on wide-ranging constitutional changes - including parity for women in a new 91-member regional assembly - has split parties on both left and right, creating uncertainty about the result. Opinion polls show that the proposals have barely a 50-50 chance of being approved.
The French president, Jacques Chirac, is an instinctive opponent of autonomy, but after a long period of hesitation he has called for a yes vote, saying a Corsican parliament with more power is the best way to ensure that the island's 260,000 inhabitants stayed French.
But the leader of the biggest separatist group, Corsica Nazione, Jean-Guy Talamoni, said the fourth constitutional revision in 25 years would accelerate independence moves by putting breakaway parties in a position to control a new administration with tax-raising powers.
Other leaders have warned that a no vote would bring a resurgence of terrorism. And whatever way the vote goes, the nationalists are likely to become more prominent.
The significance of a big influx of women into island affairs may turn out to be the most important change of all. Today, reflecting the traditionally macho society in which guns are carried openly, there is only one woman among 52 Corsican départemental (county) councillors, and there are no women MPs.
In the past 30 years more than 9,000 bombings have been carried out, underlining the repeated failure of central government to control nationalism. In calling for a yes vote, President Chirac endorsed the end of an experiment he introduced in 1976, when he was prime minister. It was then that the island was split into two départements in a vain attempt to reinforce central government control.
Scottish precedent
The départements will be reunited if the reform goes through the French national assembly in the autumn, allowing local government to be concentrated in a single regional parliament which will replace a body set up in 1986. It will control education, culture, transport, tourism and industry as well as fiscal policy.
The changes are based on a plan drawn up in 1999 by Lionel Jospin's socialist government. The right, including President Chirac,opposed the plan, but the present interior minister, Nicolas Sarkozy, adopted its broad lines after visiting the Scottish parliament, which he sees as a model for Corsica.
The original plan was a response to the most significant political assassination since the war - the shooting in 1998 of the préfet (governor), Claude Erignac, by a Corsica Nazione activist. The main suspect, Yvan Colonna, is still on the run, but eight of his alleged accomplices are on trial in Paris.
The interior minister in 1999, Jean-Pierre Chevènement, resigned in opposition to moves to give Corsicans more self-government, fearing it would signal the break-up of the republic, and he continues to lead the anti-reform movement.
"The killers wanted to force the government to negotiate, and within 18 months they had achieved their goal," Mr Chevènement said. "I fear the present government wants to hand over the key to independence movements in the new regional assembly in which they will hold all the power."
The nationalist movement, which is split into rival clans with a long history of vendettas, has been active since Genoa governed Corsica in the 14th century. After 400 years of trying to stifle rebellion, the Italian port handed authority over to the French in 1768, the year before Napoleon Bonaparte was born in the capital, Ajaccio.
IRA links
After frequent attempts to break away from France, the nationalist movement was revived in a revolt in 1976, when autonomists killed two police officers in a siege.
A Corsican national liberation front, the FNLC, was set up. It made links with the IRA and Eta before being banned. But its members formed new armed groups, sometimes connected to criminal gangs, reviving the clan rivalry in which about 100 autonomists have been shot dead in fratricidal gun battles.
Island of political storms
· Rival clans of nationalists active since 14th century when Corsica was ruled by Genoa
· Napoleon's birth in 1769 came a year after island was ceded to France
· Corsica had three years of independence before Napoleon restored French rule in 1797
· Island was occupied by Italy in 1942, and recaptured a year later by France
· Nationalists revolted in 1976. Corsican national liberation front (FNLC) set up. Island split into two administrative départements
· Low-intensity terrorist campaign reaches peak with assassination of the French préfet in 1998
· A year later socialist government proposes a new status. Plan taken up by the conservative government and put to a referendum