Desperate to consolidate the gains of the revolution in a volatile aftermath of the fall of Zine al Abidine Ben Ali in early 2011, Tunisians turned to an elderly man to steer their political transition.

Re-emerging after years in political wilderness Beji Caid Sebsi, then 84, took over as prime minister, winning popular assent in part because he was considered too old to have political ambitions.

As expected, he dutifully stepped down after constituent assembly elections in October, handing the reins of power to the winner, the Islamist Nahda party.

Political transitions in the Arab world, however, have a way of throwing up surprises. And one of them is the second comeback of Caid Sebsi. Within a year of Nahda-led rule, he was back in the limelight, this time as the leader of Nidaa Tunis, a movement created to assemble disparate liberal parties and create a counterweight to Nahda.

Today, as Tunisia faces one of its deepest political crises after the assassination of a leftist politician, the first targeted killing in the country’s modern history, the pressure on Nahda has intensified. The prime minister has called for the dissolution of the government, a move that has been opposed by his own party, but has been welcomed by the opposition.

On Monday, all three cabinet ministers belonging to President Moncef Marzouki’s Congress for the Republic Party accused Nahda of trying to monopolize political power and threatened to follow through on a threat to resign if the Islamists did not change their ways.

The fraying of the Nahda-led coalition is a sign that Tunisia’s political climate might be changing.

But can Sebsi challenge the trend of Islamist surge and threaten a party that, despite having been decimated by Ben Ali’s regime, has proved extremely adept at mobilizing popular support in elections?

His answer is an emphatic yes, of course. Polls might not be very reliable in Tunisia, but the trend is indicative. “We are going up and Nahda is going down,” he said in a recent interview with the Financial Times.

Sebsi’s effort to build a broad liberal coalition to compete in elections due by the end of the year will be watched across the region, where Islamists have had better organization and discipline, and religion, to widen their appeal.

Nidaa Tunis is a curious phenomenon which, as one rival liberal politician says, rests almost entirely on the charismatic personality of Sebsi, a no-nonsense leader who manages to project both authority and fairness.

In many ways, his appeal is the product of nostalgia for the years of the late Habib Bourguiba, the founder of modern Tunisia under whom Sebsi served as adviser and government minister.

Afraid of the impact of Islamism on a traditionally secular society and disgusted by the recent past, which was dominated by a corrupt, repressive Ben Ali regime, liberal-minded Tunisians are harking back to a time when a leader (Bourguiba in this case) turned against Islam, banned polygamy, legalized abortion and granted women more rights than anywhere else in the Arab world. That Bourguiba was also an autocrat seems, in many people’s minds, to be a detail compared to his accomplishments.

Sebsi insisted his comeback was a result of Tunisia’s political scene, which produced a strong Islamist party and scattered liberal and leftist groups. “We are Nahda’s alter ego,” he said. “Democracy is not only about elections but about the rotation of power, which can happen only if there is a balance of power.”

The slogans of the youth who launched Tunisia’s revolution were for freedom and jobs and against corruption, abuse of power and marginalization of their region, he argued. “There were no demands for religion or ideology.”

Sebsi said he has been disappointed by Nahda’s performance in government, citing the party’s early attempt to include Islamic law in the constitution, though it quickly retreated on that. He charged that the Islamists also have adopted a lax attitude toward the more puritanical Salafis as well as toward rowdy youth groups accused of attacking opposition meetings and leaders.

Nahda officials insist that they are not worried about Nidaa Tunis, with one saying that given the traditional divisions among liberals, the party will “blow up before it flies”. Nidaa Tunis, says the official, also is home to many former members of the ruling party and will therefore be rejected by voters.

Among liberals, though, the greater concern is that the party depends so much on the personality of one man. “It’s true that I’m more known than others and people saw me in government and saw that I ceded power,” Sebsi said. “I hope to have enough time to create something that will survive me and my successors.”

Additional reporting by Borzou Daragahi in Tunis.