Georgians on Sunday started voting in a presidential poll to elect a successor for charismatic leader Mikheil Saakashvili, with an ally of his billionaire foe Prime Minister Bidzina Ivanishvili favourite to win.
Giorgi Margvelashvili -- from Ivanishvili's Georgian Dream coalition -- looks likely to win the vote in the ex-Soviet state ahead of ex-parliament speaker David Bakradze from Saakashvili's United National Movement (UNM).
A combative challenge from former parliament chairwoman Nino Burjanadze -- along with a high percentage of undecided voters -- could force a second round if no candidate manages to get over 50 percent.
US-ally Saakashvili -- who has dominated the Caucasus nation of some 4.5 million people over the past decade -- has to step down as his legally allowed second term is ending.
The poll -- which OSCE monitors say is being conducted in a "notably calmer" atmosphere to previous elections -- will usher in constitutional changes that see the next president give up a raft of key powers as Georgia shifts to a more parliamentary system.
Ivanishvili -- who wrested power from Saakashvili's party at parliamentary polls last year in Georgia's first smooth transition of power -- has also pledged to name a successor and resign shortly after the vote.
Polling stations will close at 1600 GMT with preliminary results expected to come out overnight.