The north African country, which led the so-called Arab Spring, will in three weeks elect a 218-member constituent assembly tasked with drafting a new constitution for the country ahead of parliamentary and presidential polls.
The Islamist movement Ennahda (Renaissance) is considered the favourite to win the polls. The party symbolically launched its campaign in Sidi Bouzid, the town where street vendor Mohammed Bouazizi set himself on fire on 17 December in protest at police harassment, touching off a popular uprising that led to the fall of Ben Ali after 23 years in power.
Ennahda had been banned as a political movement under Ben Ali who in 2009 was re-elected with 89.6 per cent of the vote in a widely criticised election result.
His party, the Rally for Constitutional Democracy, was dissolved by a court in March.
Nearly 11,000 candidates are due to contest the elections in 27 districts, with opinion polls showing that the profusion has left voters sceptical and undecided.
Maria Espinosa, deputy head of the European Union observer mission, said she felt "confident" about the process in what she described as a "productive and transparent climate."