Tunisians voted on Sunday in a presidential run-off election that completes the country's transition to full democracy nearly four years after an uprising which ousted autocrat Zine El-Abidine Ben Ali.
With a new progressive constitution and a full parliament elected in October, Tunisia is hailed as an example of democratic change for a region still struggling with the aftermath of the 2011 Arab Spring revolts.
The North African nation avoided the bitter post-revolt divisions troubling Libya and Egypt, but Sunday's election is between a former Ben Ali official and the incumbent who claims to defend the legacy of the 2011 revolution.
Frontrunner Beji Caid Essebsi, a former parliament speaker under Ben Ali, won 39 percent of votes in the first round of voting in November with current president Moncef Marzouki taking 33 percent of the ballots.
Polling opened at 8 a.m. local time (0700 GMT) with a heavy security presence at voting stations around the capital Tunis.
Official preliminary results were not expected until Monday.
Overnight one gunman was killed and three arrested after they opened fire on a polling station in the central Kairouan governorate, a defence ministry official said.
Essebsi, 88, dismisses critics who say he would mark a return of the old regime stalwarts. He says he is the technocrat Tunisia needs after three messy years of the Islamist-led coalition government that followed the revolt.
Marzouki, 69, is a former activist during the Ben Ali era who has painted an Essebsi presidency as a setback for the "Jasmine Revolution" that forced the former leader to flee into exile.
"The revolution has to continue. Tunisia is a leader in democracy in the Arab world, but the return of the old regime could put an end to that model," Marzouki said voting in the coastal town of Sousse.
Yet many Tunisians tie Marzouki’s own presidency to the Islamist party's government and the mistakes opponents said it made in controlling influence of hardline Islamists in one of the Arab world's most secular countries.
"I am voting for a more liberal and open future, to put an end to these last three years. I wouldn't miss this historic opportunity," said Monia Ben Slimen, voting for Essebsi at a Tunis polling station.
Compromise has been important in Tunisian politics. Essebsi's Nidaa Tounes party managed to reach a deal with Islamist Ennahda to overcome a crisis triggered by the murder of two secular leaders last year.
Ennahda eventually stepped down at the start of this year to make way for a technocrat transitional cabinet until elections. But the Islamists remain a powerful force after winning the second largest number of seats in the new parliament.
Essebsi appeals to the more secular, liberal sections of Tunisian society, while analysts expect Marzouki to draw on support from more conservative rural areas, and from members of Ennahda, which did not field a presidential candidate.
The presidency post holds only limited powers over national defence and foreign policy. In Tunisia, the parliament, led by Essebsi's Nidaa Tounes party which won the most seats, will be key to selecting a new prime minister to lead the government.
Ennahda and the leftwing Popular Front movement, both well-organised, would be powerful opponents to Nidaa Tounes in the parliament, making more compromise deals likely. Whoever wins, Tunisia's new government must tackle the threat posed by Islamist militants as well as potentially politically sensitive economic reforms in a country where many are still worried about jobs and the high cost of living.