Bolivia's President Evo Morales is likely to see his reforms approved
By James Painter
BBC Latin America analyst
Bolivians go to the polls on Sunday to vote in a referendum on a new constitution, which would make permanent a number of radical changes promoted by left-wing President Evo Morales.
It is the second time in six months that Bolivia has voted.
Last August, Mr Morales won 67% of the popular vote in a recall referendum on his presidency, up from the 54% he won in the December 2005 presidential elections.
His continuing popularity, and divisions within the opposition, mean that the Yes vote is very likely to win this latest poll.
But there is plenty of room for disagreement over the implementation of the new constitution, and disputes between the government and the right-wing opposition look set to continue regardless.
Bolivia's Congress approved holding a referendum only after Mr Morales agreed to make a number of concessions.
Crucially, Mr Morales agreed to restrict his candidature as president to a single five-year term.
Under the current 1967 constitution, no president is allowed to have two consecutive terms. This was due to be changed under the original draft text, prompting fears from the opposition that Mr Morales could stay in office until 2019.
Under the new constitution, Catholicism would no longer be the official religion
But in a key concession, the president promised to stand just once more in elections due in December this year if the new constitution is approved.
This means that he is still likely to stay in power until 2014, but he says no longer.
He also made other concessions on autonomy, land reform and Congressional voting procedures.
Nonetheless, in his view, the key changes - extending the rights of Bolivia's 36 indigenous groups and strengthening state control over the country's natural resources - remain broadly intact.
When agreement was reached on the concessions back in October, Mr Morales wept in front of a huge crowd of supporters in La Paz's Central Plaza, where Indians were not allowed to set foot until the 1950s.
"We have made history," he said. "I can now go to the cemetery a happy man."
Among the 411 articles of the new constitution, some of the key changes provide for:
• A mixed economy which recognises public, private and communitarian ownership. However, the state will control natural resources such as oil, gas and minerals
• The state as unitary and pluri-national, designed to stress the importance of ethnicity in Bolivia's make-up. A whole chapter of the draft text is devoted to indigenous rights
• Power will be decentralised, creating four levels of autonomy - departmental, regional, municipal and indigenous
• Indigenous systems of justice will be given the same status as the official existing system. Judges will be elected, and no longer appointed by Congress.
In a further concession, Mr Morales agreed that new limits on land ownership will not be retroactive - a parallel referendum on Sunday will determine whether this limit should be set at 5,000 (12,355 acres) or 10,000 hectares (24,700 acres).
But even if the vote is in favour of 5,000 hectares - and there are many farms in the east larger than this - landowners will not be affected if they can show that their land is not idle and fulfils a social and economic function.
However, Mr Morales' opponents say that since it will be up to central government to decide if landowners are complying, the system could be open to abuse.
Another controversial change to the constitution is that Catholicism would no longer be the official state religion - there would be no state religion.
The Church has also criticised the new draft text for not recognising the right to life from conception (possibly opening the way to legalising abortion), although the existing constitution does not either.
Some bishops have joined with the opposition in campaigning against the constitution. One of their slogans says "Choose God, Vote for No".
Most analysts say that despite making a number of concessions, Mr Morales remains in a strong position.
They point out that the opposition is split between more moderate members of the Congress and the more confrontational governors of the four, mainly eastern, departments known as the media luna, or half-crescent.
"The balance of power shifted," says George Gray Molina, a research fellow at Oxford University in the UK.
Protests against the government have sometimes turned violent
"Evo has already won the referendum vote. The opposition will probably retrench for a while with an eye on providing a unitary candidate for the December [presidential] elections," he says.
However, there is plenty of room for continuing opposition from the four media luna departments, which tend to be wealthier and more ethnically mixed than the mainly indigenous departments of the western highlands. They want more autonomy from the central state.
They also contain most of Bolivia's natural gas production and agribusiness, such as soya.
There are two main issues over which opposition civic organisations can continue to fight.
The first is whether their departments will have priority over the other three levels of autonomous organisation envisaged in the new constitution.
Another is how the taxes on gas exports will be divided up between the state and the four levels of autonomous organisations.
"The civic groups in Santa Cruz and Tarija, in particular, will continue to demand a bigger share of the proceeds of gas exports," says John Crabtree, an analyst at the Oxford Centre for Latin American Studies in the UK.
"While the new constitution may now be legally enacted," he says, "battles are looming over how its provisions are finally applied."