TUNIS — Tunisia’s moderate Islamist political party emerged Monday as the acknowledged leader in elections for a constitutional assembly and began talks to form a unity government with a coalition of liberals in a rare alliance that party leaders hailed as an inclusive model for countries emerging from the tumult of the Arab Spring.

By Monday afternoon, Tunisian liberal parties said they were entering discussions to form a government led by their Islamist rival, Ennahda, after it swept to a plurality of about 40 percent in preliminary vote tallies. The acceptance of the results by rivals signaled the beginning of a partnership seldom seen in the Arab world, where Islamists’ few opportunities for victories at the voting booth have sometimes led to harsh crackdown or civil war.

In neighboring Algeria, an electoral victory by Islamists 20 years ago set off a military coup and a decade of bloodshed, and in the Palestinian territories, the sweep to victory of Hamas in 2006 elections led to a showdown with the West, a split in the government and armed conflict in Gaza.

Tunisia’s was the first election of the Arab Spring, held to form an assembly that will govern while it writes a constitution, 10 months after the ouster of President Zine el-Abidine Ben Ali.