Resurgence of revolt where Arab Spring began
As dozens of riot police fired volleys of tear gas towards crowds of angry youths on Bourghiba Avenue this week, the scene was disturbingly reminiscent of what happened on this very avenue two years ago.
Even the chanting was the same: "We want the downfall of the regime!"
The target of the crowd's anger may be a different government, but many here feel their efforts in 2011, when they succeeded in removing Zine al-Abidine Ben Ali, may have been for nought.
Many outsiders, myself included, always believed the Tunisian "Jasmine" uprising had the best chance of succeeding, of building a vibrant new democracy, above all the other subsequent Arab revolutions.
Tunisia has a large civic society and almost everyone goes to school until the age of 16. French is widely spoken, in the big cities at least.
After elections to a constituent assembly, the winning Ennahda party - though allied to the Muslim Brotherhood - promised to be inclusive, and brought in several liberal elements into its interim administration.
But, as in Egypt, liberal and secular Tunisians are discovering that democracy is not so easily won.
The murder of leftist secular politician Chokri Belaid may have come as a shock to most Tunisians, but there have been underlying tensions here for months.
Belaid, in many ways an old-fashioned socialist, was also a vocal opponent of Ennahda's governing coalition.
Although Ennahda portrays itself as a moderate and tolerant body, the government's critics say that in recent months it has allowed ultraconservative Muslim groups, or Salafists, to impose their will and opinions on what was always regarded as a bastion of Arab secularism.
Salafists have stopped music concerts, disrupted art shows, ransacked the US embassy (ostensibly in anger at a film which portrayed the Prophet Muhammad in a negative light) and have protested violently at universities.
The day before he was killed - shot four times as he left for work - Belaid had warned there was a climate of systematic violence sweeping across the country and threatening the revolution's many gains.
His murder "deprives Tunisia of one of its most courageous and free voices", said French President Francois Hollande.
His funeral on Friday in central Tunis is bound to be an emotional, angry event. Members of the government have been warned to stay away.
And even though political leaders have responded by saying they will form a unity government made up of technocrats until new elections are held, more trouble is expected in towns across Tunisia in coming days.
This country of 11 million people is again at a crossroads.
The state of the economy, which relies heavily on "fickle" markets like tourism worries everyone.
Overseas interests - in particular French companies - continue to base themselves here and are a vital part of this country's future. If they were to be frightened off by political instability, those positive signs we all saw two years ago would begin to fade.
It is easy to see a scenario in which everything quickly deteriorates.
In the last 24 hours there have been disturbing reports of widespread looting and rioting in provincial towns, including Sfax. Young men, probably not ideologically allied to either the Islamists or the opposition, have quickly vented their anger and dissatisfaction.
Yet, the fact that thousands of citizens - young and old, man and women - care so much about the assassination of a liberal politician, also speaks volumes.
These Tunisians are desperate to avoid the polarising chaos that has plagued other countries in the region, in particular Egypt.
Most Tunisians are proud of the fact this was the place where the Arab Spring was born, but they are also determined it is not where it will prematurely die.