Georgian opposition leader Bidzina Ivanishvili is known in the former Soviet republic as a once-poor, now-billionaire philanthropist who backed President Mikheil Saakashvili before his crackdown on public dissent and the 2008 territory war with Russia.

Ivanishvili, who leads the opposition Georgian Dream coalition, is now poised to become prime minister, a position that will gain much more power when Mr. Saakashvili finishes his final term next year. The Georgian constitution mandates that some presidential powers be handed over to the prime minister at that time.

The opposition leader says he, like the president, supports Georgia joining NATO and the European Union, but he also wants to mend ties with Russia.

The 56-year-old Ivanishvili, reported by Forbes magazine to have a fortune of some $6.4 billion, is known for keeping exotic animals, collecting art, and funding various improvement projects in the poor region of Georgia where he grew up. Before his relationship with Mr. Saakashvili soured, Ivanishvili even used his fortune to buy supplies for soldiers in Georgia's army.

Ivanishvili made much of his fortune building various businesses in Russia, leading to criticism from Mr. Saakashvili that his rival is too strongly tied to Moscow and Russia's President Vladimir Putin. Ivanishvili has sold all his Russian businesses since joining the political competition.

But he says his ties to Russia — compared to the icy relationship between Mr. Saakashvili and Mr. Putin — will benefit Georgia diplomatically and economically.