TUNIS (AFP) ― The battle for an expected runoff vote for the Tunisian presidency kicked off Monday even before first round results were in from a landmark post-Arab Spring election.

Veteran anti-Islamist politician Beji Caid Essebsi, whose party placed first in a parliamentary election last month, looked set to fall short of the 50 percent threshold required to win outright, his campaign team conceded.

He is poised to face off against incumbent Moncef Marzouki, a secular politician who has made common cause with the Islamists against what he says is an attempt at a comeback by former loyalists of the autocratic regime overthrown in 2011.

Wasting no time in relaunching the battle after Sunday’s vote, Essebsi said his rival was the candidate of “jihadist Salafists,” to which Marzouki countered by calling for “a debate on policies ... not (a campaign of) insults.”

Election officials, who announced a turnout of 64 percent, have until Wednesday to publish the official results.

The election is a milestone for the North African nation, whose ouster of longtime strongman Zine El Abidine Ben Ali set off a chain of revolts that saw several Arab dictators toppled by citizens demanding democratic reform.

U.S. Secretary of State John Kerry hailed an “historic moment” in Tunisia’s transition to democracy, and pledged Washington’s support for the next government, whoever leads it.

His French counterpart, Laurent Fabius, called for Tunisia’s transition toward building new institutions to remain “inclusive and democratic.”

Tunisian leaders pride themselves on the fact the country has been spared the bloodshed that has ravaged other Arab Spring states such as Libya and Yemen.

Despite fears of disruption by Islamist militants, polling day passed off peacefully.

Neighboring Algeria, which survived the turmoil of the Arab Spring after a few days of rioting in January 2011, welcomed the vote.

“This vote marks a decisive step in the process of democratic transition,” said Foreign Ministry spokesman Abdelaziz Benali Sherif.

But the expected runoff scheduled for late December is likely to be polarizing, with Marzouki’s camp portraying him as the last line of defense against a return to the autocratic ways of the old regime, and his opponent deriding him as an Islamist pawn.

In a speech, Marzouki called on “all democratic forces” to back him against Essebsi, who served under both Ben Ali and his predecessor Habib Bourguiba.

“I am now calling on all democratic forces ... alongside whom I have campaigned for the past 30 years for a real democracy, for a break with the past, for a genuine civil society and for a separation of powers.”

Marzouki argues that only he can preserve the gains of the uprising, while his critics say he hijacked the spirit of the revolution by allying himself with the moderate Islamist party Ennahda in 2011.

The rule of Ennahda, which came second in the October parliamentary election, was marred by a surge of radical Islamism and the assassination of two leftist politicians by jihadist suspects.

Essebsi insisted on Monday that only he could defend Tunisia against the threat of Islamist extremism.

“The people who voted for Marzouki were the Islamists ... that is to say Ennahda members ... but also the jihadist Salafists,” he told French radio station RMC.

Asked about the likely runoff, Essebsi said: “Unfortunately there is going to be a split down the middle, with Islamists on one side and then all the democrats and non-Islamists on the other.”

If Essebsi wins he will have to form a coalition government, even with Ennahda, because his Nidaa Tounes party fell short of securing an absolute majority in October.

The rival camps disagreed over their balance of support as a runoff loomed.

Marzouki’s camp said he was neck and neck with Essebsi, the pre-polling favorite for the top job, while his rivals said the Nidaa Tounes chief was well ahead.

Another presidential hopeful, leftist politician Hamma Hammami, who according to exit polls came third, told the media his political group would meet “as soon as possible” to consider how to vote in a runoff.