Voters in Sierra Leone are going to the polls to elect a successor for President Ernest Bai Koroma in a campaign where the participation of an unprecedented number of political parties is making the outcome too close to call.

As Koroma nears the end of his second five-year term, the nation of 6.5 million people will select among 16 candidates for a leader that can revive an economy that’s been wrecked by the worst outbreak of Ebola and a slump in prices of iron ore.

Koroma chose former Foreign Affairs Minister Samura Kamara as the ruling All People’s Congress candidate, who will compete against the opposition Sierra Leone People’s Party’s Julius Maada Bio. A newcomer, the National Grand Coalition, is expected to win a significant amount of votes, raising the probability of a runoff as no candidate is expected to secure 55 percent in the first round.

“The grip on power that the APC has is under threat,” Jamie Hitchen, an independent analyst, said by phone from the capital, Freetown. It is difficult to forecast “what will happen in the likely event of a runoff; it’s really hard to know how the other political parties will realign themselves,” he said.

Polls open at 6 a.m. and the outcome is likely to be announced by the weekend.

In 2012, Sierra Leone was sub-Saharan Africa’s fastest-growing economy as Chinese and U.K.-based investors began developing its iron-ore reserves. But the double shock of a commodity price slump and the worst-ever Ebola epidemic the following year triggered the collapse of the two iron-ore mines in the country and left the economy in ruins.