Syria has been one of the foundations of Iran's regional strategy not only because of its geopolitical influence but also because of its similar authoritarian model.
Iranians opposed to their regime are now holding out some hope for change, especially after the brutal suppression of a women's rebellion in recent years, in which hundreds of citizens have been killed and thousands arrested.
The changes in Syria therefore prompted Supreme Leader Ali Khamenei to issue an official warning.
"Anyone whose analyzes or statements discourage the people is committing a crime and will be prosecuted. "Some are doing it from abroad using Persian-language media, but no one inside the country should behave like that," Khamenei threatened last week.
Some interpret it as the religious regime's fear of a domino effect. In addition, Iran has been in a severe economic crisis for a long time and is losing allies in the region, which further alarms the regime.
Supporters of the regime in "shock"
Hossein Razag, a political activist who has been arrested several times since the Green Movement in Iran in 2009, believes that the fall of Assad has particularly upset the regime's hardliners in Tehran.
As he says, the regime elite with their families, as well as those connected to the military and the religious establishment, are now doing their best to ensure the survival of the regime in Tehran.
"The collapse of Assad sent hardliners in Iran into a state of shock," Razag told DW. "It also shook the propaganda machinery of the Islamic Republic. Many of its die-hard supporters are now questioning whether Iran is also on the verge of collapse."
Razag believes that the drop in credibility of the leadership in Tehran is unprecedented, much greater than during earlier waves of protests.
"The psychological state of society is such that any spark - say, Khamenei's death or some other blow - can be the starting shot for the fall of the regime."
Legitimacy rots from within
Hasan Asadi Zeidabadi, another political activist from Tehran, points out how disappointed people are with the government's inefficiency and corruption.
"A crisis of legitimacy and competence led to Assad's fall," he says. "The same goes for the Iranian authorities, who are finding it increasingly difficult to meet even the basic needs of citizens."
Zeidabadi mentions fuel shortages, electricity and internet restrictions, and air pollution, which causes Tehran to regularly sink into smog.
And Mehdi Mahmudijan, another activist and former political prisoner, points out that citizens increasingly realize that the regime cannot ensure economic recovery.
"The regime has lost its legitimacy and ability to function. In addition, Assad's fall means that Tehran has little material left to negotiate with the West."
Mahmoudian blames the West for keeping the country under economic sanctions that harm ordinary people. He calls for the top of the regime to be the target of the sanctions.
"Instead of direct intervention, Western countries should concentrate on strengthening civil society in Iran," he says.
Despite many sensing the end of the regime, Zeidabadi says it is still a long way off. "Although the geopolitical and historical dynamics of the Middle East link the destinies of individual countries, this does not automatically mean that Iran will be the next domino."
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