The second national referendum on the issue of abortion will be a major day in Portuguese political and social life.
Portugal has restrictive abortion laws. Until 1984, abortion was considered a criminal offence and women who had an abortion could face up to eight years in prison.
Today abortion is legal if a woman is pregnant as a consequence of rape, in cases of probable birth defects or serious illness of the foetus or if the pregnancy endangers the woman's health.
In 1998, parliament voted on a woman's right to choose to have an abortion up to ten weeks into her pregnancy.
The proposal was won by one vote. But both the Socialist Party (SP), which is similar to Britain's Labour Party, and the liberals (PSD) agreed that the issue should be decided by a referendum.
The referendum took place in June. The right wing parties called for a no vote. The Catholic church launched a vicious anti-abortion campaign, showing images of nearly full-term babies, saying they were of embryos.
The Socialist Party split with the then prime minister, Antonio Guterres, declaring he was against changing the law.
Only 31.9 percent voted. This was a massive abstention by Portuguese standards, where the average turnout is usually over 60 percent. Some 50 percent voted no and 48 percent voted yes.
At that time, one of the main arguments used by the right was that, in spite of abortion being considered a criminal offence by law, no women had yet been put to trial. This is no longer the case.
The political situation today is very different. Only the populist right CDS Party is clearly campaigning for a no vote.
The PSD has given its members a free vote, and the SP has taken part in the yes campaign, with prime minister Jose Socrates and several members of the cabinet directly involved.
The no campaign has been able to mobilise the conservatives and the church is pursuing an aggressive anti-choice campaign.
But there are also several pro-choice groups which are very active. The Left Bloc is having its own campaign centred on the question of the abortion trials, with the slogan 'Vote Yes To Put An End To Women's Humiliation'.
We face the most difficult campaign since the formation of the Left Bloc. A yes vote will not just be a victory for women's rights, but will also show the possibility of victory against conservatism – after so many years of defeats.
This could also start a new era of a different mood for the workers and the left.
Alda Sousa is a member of the national executive of the Left Bloc in Portugal.