Leonid Tibilov, who led the region's KGB before falling out with the former local president, won over 40 percent of the vote in the first round last month. Tibilov is expected to easily defeat his rival in the runoff, presidential human rights commissioner David Sanakoyev, who polled 25 percent in the first round.
South Ossetia depends entirely on subsidies from Russia, which recognized it as an independent state after the 2008 Russian-Georgian war and still has troops there. The ties with Moscow are expected to remain close no matter who becomes president of the province, which has a population of about 50,000.
Only a handful of other countries have followed Russia in recognizing South Ossetia's independence, while a Georgian economic blockade and misappropriation of lavish Russian aid have left the regional economy in shambles with widespread poverty and massive unemployment.
Critics accused the government of former President Eduard Kokoity of embezzling Russian donations, while thousands of South Ossetians continue to live in half-destroyed houses and apartment buildings with irregular water and electricity supplies.
South Ossetia first tried to elect a new president in November, when former education minister Alla Dzhioyeva appeared to have beaten a rival backed by the Kremlin and the former local president, but the results were disputed and a local court ordered a new vote.
The mountainous province broke away from Georgia in a war in the early 1990s. Spiraling tensions between Georgia and pro-Russian separatists triggered the August 2008 war, in which Russian troops routed the Georgian military in five days of fighting.