Born in a Georgian village, Mr Ivanishvili made his fortune in Russia, amassing assets from banking and mining to hotels. In 2003 he returned to Georgia, where he has since been a secretive philanthropist, paying artists' salaries, restoring churches and museums and building the country's biggest cathedral. His hilltop fortress, complete with helicopter pad and water cascade, is guarded by a small army of security men, as if it belonged in a Bond film.
Mr Ivanishvili wants to make Georgia a democracy to "astonish the world". But his motives are murky: is he just seeking power, is he acting from fear of (or with encouragement from) the Kremlin, or does he really wish his country well? He claims his family persuaded him. "My son threatened me that if I don't get into politics, he will." Having "studied" the opposition, he realised it was "incapable". But he has sought the help of some of its leaders, including Irakly Alasania, a former Georgian ambassador to the United Nations.Mr Ivanishvili talks of Georgia as if it were a venture-capital project he might run for a year or so, installing an independent judiciary, free media and good managers. "He sees it as a hostile takeover," says Kakha Bendukidze, a businessman and reformer. Mr Ivanishvili's first aim is to dent Mr Saakashvili's global reputation. "Nobody really likes him in Europe and in America...you will see [his Western support decline] in two to three months."He denounces Russia's aggression towards Georgia over the breakaway (and, as a newly disputed election shows, still troubled) region of South Ossetia in August 2008. But he blames Mr Saakashvili for starting the war. He is cautious when talking of Russia's prime minister, Vladimir Putin. Georgia, he says, is less democratic than Russia and has no right to lecture its neighbour. As for the West, "nobody wants to fall out with Russia over Georgia."Mr Saakashvili has been more reformer than democrat. Georgia's courts lack independence, the police are politicised, parliament acts as a rubber stamp, media ownership is opaque and the government is intolerant of critics. Yet he has transformed a failed state into a modern country with a liberal economy and a strong credit rating. He affects to be relaxed about his challenger, saying "Ivanishvili is good for us, he will keep us in good shape." Observers agree that Georgia needs more political competition, but not a new upheaval.Mr Ivanishvili says he will "definitely" win a big majority in the parliamentary election next year. He has an eye on the premiership. Yet his popularity rating is only 17% against 42% for Mr Saakashvili's party. Mr Saakashvili's job approval-rating is higher still. The government is confident that Mr Ivanishvili will not eat into its core vote, but fears he may dispute the results on the streets. Mr Ivanishvili insists he has no wish for a revolution, but he is prone to changes of mind.
Not long ago he pledged to impeach Mr Saakashvili in parliament. But he now says "in fact, I don't think I will want impeachment." He talks little of what ordinary Georgians want.His main appeal is his wealth. There is a danger that Georgians will see him as another saviour. He has support among the intelligentsia and from the influential Georgian church. Yet the biggest risk lies not in his challenge but in the response it is provoking. The government has stripped Mr Ivanishvili (and his wife) of their citizenship on a pretext and seized a few million dollars from his bank. This smacks of harassment and panic. A key question is what will happen when Mr Saakashvili's term expires. Mr Ivanishvili claims that Georgia's constitutional change from a presidential to a parliamentary system is a strong hint that Mr Saakashvili wants to stay in power as prime minister.
Mr Saakashvili does not yet show any sign of following the example of Mr Putin in Russia in this way, knowing it would destroy his reputation and legacy. "It is more important for him what kind of Georgia he leaves behind than what he personally does," says Giga Bokeria, his national security adviser. But that legacy depends on the continuity of his course and team, and so on stopping Mr Ivanishvili. The next two years may not be so dull after all.