Ennahda, as the biggest party in parliament, has now until Friday to name its nominee for prime minister.
The new parliament in Tunisia elected Wednesday Rached Ghannouchi, leader of the Islamist Ennahda party, as its speaker after its rival party Heart of Tunisia party backed him; making a possible coalition government between the two parties more likely to happen.
It was not immediately clear what price if any, Heart of Tunisia asked for supporting Ghannouchi as a speaker.
“The party decided to vote for Ennahda after an agreement,” said Ridha Charfeddine, a Heart of Tunisia lawmaker.
The party led by media magnate Nabil Karoui and Ennahda have presented themselves as ideological rivals and have both previously rejected the possibility of entering into a coalition.
Ennahda, as the biggest party in parliament, has now until Friday to name its nominee for prime minister, starting the clock on a two-month process for that person to form a government.
Tunisia’s post-revolution constitution splits power between the newly elected President Kais Saied and a government that passes legislation through the parliament.
Wednesday’s election for speaker represented a big test for Ennahda, which was banned before Tunisia’s 2011 revolution but has since played a big role in several coalition governments.
The Islamist party came first in last month’s parliamentary election, but only won 52 of 217 seats in a deeply fragmented parliament, forcing it to negotiate to win majority support for its preferred candidates for speaker and for prime minister.
However, its efforts to build a coalition with several rival parties have so far come to nothing and the North African country continues with a caretaker government under the current prime minister, Youssef Chahed.
Tunisians voted last month for a new parliament but quiet polling stations had given an indication of the economic disillusionment that has emerged since 2011.
The failure of repeated coalition governments that grouped the old secular elite and Ennahda to address a weak economy and declining public services has dismayed many Tunisians.
"After the revolution, we were all optimistic and our hopes were high. But hope has been greatly diminished now as a result of the disastrous performance of the rulers and the former parliament," Basma Zoghbi, a worker for Tunis municipality, had said before last month’s election.
Unemployment, 15 percent nationally and 30 percent in some cities, is higher than it was under the former autocrat, Zine El-Abidine Ben Ali, who died earlier this year in exile in Saudi Arabia.
Inflation hit a record 7.8 percent last year and is still high at 6.8 percent. Frequent public sector strikes disrupt services. Financial inequality meanwhile divides Tunisians and the poverty of many areas has become an important political theme.
Any government that would be formed will face the competing demands of improving services and the economy while further reining in Tunisia's high public debt, a message pushed by international lenders.