Tunisia's national assembly on Friday began voting on the long-delayed new constitution, which must be adopted by January 14, the third anniversary of the 2011 revolution.
Adopting the new charter would be a crucial milestone in the birthplace of the Arab Spring, where hopes of a successful democratic transition contrast starkly with other countries in the region rocked by regime change.
At Friday's opening session, lawmakers approved, by 175 votes out of the 184 MPs present, the title of the charter, which also has to be voted on article by article.
"We have had difficult moments, marked by a lack of trust. It is a complicated step which requires sacrifices and patience," said parliamentary speaker Mustapha Ben Jaafara before voting began.
Elected in October 2011, just months after the ouster of long-time autocrat Zine El Abidine Ben Ali, the national assembly was due to have drafted and adopted a new charter within one year.
But the process was heavily delayed by deep divisions between the ruling Islamist party Ennahda and the opposition, aggravated by a rise in attacks by Islamist militants and sometimes violent social unrest.
The deadlock, which became a full-blown crisis with the assassination last July of opposition MP Mohamed Brahmi by suspected jihadists, paralysed political life and prevented the formation of functioning state institutions.
Ennahda and the main opposition coalition negotiated a series of compromises in recent weeks, during intense last-minute negotiations, aimed at securing the approval of two thirds of the assembly's 217 elected members needed for the constitution to be adopted.
Otherwise it must be put to a referendum.
If the charter is approved by the January 14 deadline, it could help end the political impasse.
A technocrat premier
The new constitution, and adopting an electoral law and commission, should lead to the departure of the outgoing Islamist-led government and the appointment of technocrat premier Mehdi Jomaa, nominated in December under a deal to end the crisis.
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Lawmakers will examine the text's preamble before scrutinising the 146 articles finalised in June and some 30 key amendments drafted during the latest negotiations.
Another 200 amendments have been proposed, including an attempt to make Islamic sharia law a main source of legislation, but they have little chance of succeeding.
During the negotiations, the parties agreed to keep the main article of independent Tunisia's first constitution, in 1959, which gives Islam a vague status, after Ennahda renounced its demand that sharia be enshrined in the text.
"Tunisia is a free, independent and sovereign state. Islam is its religion, Arabic is its language and it is a republic," the article says.
Another key compromises concerns the powers of the head of state, in a country that recently emerged from five decades of dictatorship.
The Islamists, persecuted under Ben Ali and who had argued for maximum limitations, finally agreed to a division of power between the president and government.
The president, who is directly elected, will also be able to propose a vote of no confidence in the prime minister and have limited rights to dissolve parliament.
On human rights, the draft text guarantees freedom of expression and of conscience, freedom of assembly and the right to strike.
"The constitution will be one of freedom, of independence and of justice," Ben Jaafar promised on Thursday, amid high hopes among politicians that the charter represents a key step towards Tunisia becoming the Arab world's first true democracy.
However, rights organisations jointly warned that some constitutional provisions were too vague.
"Among the most urgent modifications required is a clear indication that the human rights charters ratified by Tunisia are obligatory and take precedence over national laws," said the group, which included Amnesty International and Human Rights Watch.
It also called for a provision stating the principle of equality between men and women.