I write these lines to you from a maximum-security Turkish jail – which must surely be a strange idea for anyone who lives in a stable democracy. In any country where parliamentary democracy functions properly, members of parliament and leaders of political parties are not put in prison for their policies. No matter how critical they are of the government, no matter how effectively they work to oppose government, elected people are not arrested for their political views.

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But I was arrested 20 months ago when I was a member of parliament and co-chair of the HDP - the People’s Democratic party, and third largest in the Turkish parliament – which represents the will of 6 million voters. It was a year after my arrest before I was finally seen by a judge. According to the indictments served on me, I am charged with criminal offences carrying a combined sentence of 183 years.

Before becoming a parliamentarian, I visited county prisons as a human rights advocate to report violations of prisoners’ rights. However, seeing the prison walls as a lawyer and being held as a political hostage behind them is a very different experience. Over the last 20 months I have never lost my faith in democratic opposition in Turkey. Nelson Mandela wrote in his autobiography about what it meant to be a political prisoner: “The prison itself is a great education for the need for patience and perseverance. Above all, it is a test of faith/stability for people.“ Now I’m going through the training and stability test just like tens of thousands of others now in Turkey’s prisons, just for exercising the right to express an opinion and to organise.

I am now standing as one of six candidates for the Turkish presidency in tomorrow’s elections, conducting my campaign directly from my prison cell. That decision stems from the belief that the fight against the authoritarian regime operated by the president, Recep Tayyip Erdoğan, is the only way to restore peace and democracy in Turkey. I am of course aware of the limits of delivering messages to the outside through lawyers, the only means available to me. Yet, despite these limits, and a government that controls 90% of the mainstream media, the people, especially young people and women, are campaigning energetically on my behalf.

Almost all the candidates running against Erdoğan have carried out impressive campaigns. And despite their ideological differences, they are motivated by three important truths.

First is the belief that Turkey is too big to be managed by one man, especially given its surviving culture of democracy. We have all clearly seen the price of Erdoğan’s monopolisation of power over the last three years. Not only are we embroiled in persistent struggles with the west, we are dealing with multiple domestic political and economic crises.

Second, all those standing against Erdoğan believe the president lacks the courage to compete on equal terms with me, and all have condemned my imprisonment.

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Third, and most important, they detect that the people of Turkey now have a significant desire for change. Whichever party they may be from, the collective unhappiness of voters – impossible to measure with opinion polling, but encountered only in authoritarian regimes – is deeply felt.

The government of Erdoğan’s AKP party has masterfully deceived nationalist and conservative voters by blaming the west for all kinds of negative developments. The indifference shown by many Turkish people to Erdoğan’s election campaign is the clearest evidence of the winds of change. I believe that people’s understanding about who is really to blame for Turkey’s woes will be reflected in the result tomorrow.

Let’s not forget, authoritarian regimes eventually collapse. Sometimes it happens quickly; other regimes take longer to dislodge.

• Selahattin Demirtaş is the presidential candidate for the People’s Democratic party (HDP) in tomorrow’s Turkish presidential elections