TUNIS — Rachid Ghannouchi, the head of Tunisia's main Islamist party and speaker of parliament, wanted to make something clear — that a social democratic party based on Islam can still play ball in Tunisia and in the Arab world.

Thousands of his partisans had flooded downtown Tunis on Saturday in what some observers called one of the largest demonstrations in the past decade. Men, women and children backing his party, Ennahda, had been bused in from throughout the country. Draped in Tunisian flags, they chanted “National unity!” and slogans in support of Ghannouchi.

“We wanted to send a message that the revolution is still here and powerful and working, so that everyone knows their size,” Ghannouchi said in an interview a day later in his Tunis home.

Ennahda had officially called the march in support of national unity and independent prime minister Hichem Mechichi’s embattled government. Asked whether it also aimed to project his party’s power, Ghannouchi replied: “Of course.”

In a region where authoritarian governments have crushed or co-opted Islamist movements, Ennahda has sought to fashion itself an example of compatibility between Islam and democracy. It has remained Tunisia’s most resilient and influential political force in the decade since the Arab Spring. But now, as political and economic crises batter the country and Ennahda slips in the polls, the party is fighting to assert its relevance.

Ghannouchi, 79, has helmed the movement for four decades. He co-founded Ennahda’s precursor in 1981 as a nonviolent Islamist group that advocated participation in democracy. He spent several years in prison in the 1980s under Tunisian leader Habib Bourguiba before fleeing to London, where he lived in exile for more than 20 years.

After the revolution, Ghannouchi returned to Tunisia to a hero’s welcome. But he opted not to run for national office, instead serving as a power broker and guiding his party’s rise to prominence, its efforts to draft Tunisia’s new constitution and its alliances with secular parties in pursuit of a “consensual democracy” in which Islamists are major players.

“We have been convinced that we have to work with secularists to compete against any sort of fundamentalism, whether based on Islam or based on secularism,” he said Sunday, sitting in a home office lined with copies of the Koran and books such as “Religion and State in the Modern Islamic Context.”

Ghannouchi insisted that his party offers a paradigm for others in the region. The compromises it made for Tunisian democracy — and, crucially, for its own political survival — enabled it to escape the fate of the Muslim Brotherhood in Egypt, which came to power after the Arab Spring only to be crushed by a military coup in 2013.

Fearful of such a turn, Ennahda distanced itself from other Islamist groups — and from the “Islamist” label itself. In 2016, the party rebranded itself as “Muslim democratic” and banned preachers from running for office. Ghannouchi now sees the term “Islamist” as an imprecise label of little utility.

“It puts under one umbrella people who reject violence with people connected to terrorism,” he said. “This term doesn’t mean anything — it only serves to muddy the waters.”

The party’s popularity has waned over time. In 2019, it won 52 seats in the 217-seat parliament, compared with a high of 89 seats in 2011.

Ghannouchi won a seat in 2019 and was quickly elected speaker. His tenure has been marked by controversy, with the highly fragmented parliament roiled by political spats over forming a government.

Mechichi, backed by Ennahda and two allied parties, was the third head of government nominated since the 2019 election, and he is currently locked in an unprecedented constitutional dispute with Tunisian President Kais Saied that threatens to bring down the government.

Ennahda, meanwhile, faces mounting criticism from all sides. A wave of protests swept the country in January as Tunisians expressed their anger at police repression, economic difficulties and parliament. Anti-Ennahda and anti-Ghannouchi slogans abounded, as well as calls for parliament’s dissolution and “the fall of the regime.” The heavy-handed police response drew condemnation from rights groups but little concern from Ennahda.

“There are some real grievances, but I believe these grievances are being used by some radical political parties,” Ghannouchi said of the protests.

“If you put our experience in context with other Arab Spring countries . . . it’s a model experience of democratic transition,” he added.

Still, Ghannouchi acknowledged that his party bears some blame for a failure to address worsening economic conditions.

“We take responsibility proportionally to our size in government,” he said. “There’s no doubt that our experience in governing was minimal. There’s no doubt that we have learned a lot from our experience.”

Ever the polarizing figure, Ghannouchi has seen his popularity plummet as his four-decade career in politics winds to a close. His public approval rating now stands at 8 percent. Divisions within Ennahda over his leadership exploded into public view in the fall, when 100 leaders signed an open letter urging him not to seek another term.

Ghannouchi’s position in parliament is also in jeopardy — a motion of no confidence against him had garnered 103 signatures as of last week, a lawmaker told Tunisian media. Ghannouchi said he does not expect the motion to pass, “but if it happens, it’s not the end of the world.”

The political turmoil has worsened Tunisia’s deepening economic crisis and spooked investors. The fallout from the coronavirus devastated Tunisia’s already struggling economy, which contracted by an estimated 8.2 percent in 2020, according to the International Monetary Fund.

Hopeful that the Biden administration might come to the rescue, Ghannouchi has made overtures to the United States in recent weeks, including meeting with U.S. Ambassador Donald Blome and penning an op-ed in USA Today.

“The success of Tunisia’s democracy is in the interest not just of Tunisia but of the world,” he said Sunday, “because it’s an example of where Islam and democracy are compatible and it’s the best way to fight extremist interpretations and violent interpretations.”