Vladimir Putin's surprise appointment of a political unknown as Russia's new prime minister has further complicated the question of who will succeed him as the country's president when Putin's second (and constitutionally last) term ends in March 2008. Recent polls show that more than 50 percent of Russians will vote for whomever Putin endorses. But predicting who his pick will be is tricky because the Kremlin's inner circle is even tinier and more secretive than it was in the Soviet era. The new prime minister, Victor Zubkov, 66, the former head of Russia's financial-regulation agency, is a close comrade of Putin's from St. Petersburg in the early 1990s. Still, Putin favorites Sergei Ivanov, Russia's former Defense minister, and Gazprom gasmonopoly head Dmitry Medvedev remain front runners. The key for Putin, says his former chief of staff, Aleksandr Voloshin, is "to feel that he has the option to return to power" for a third term as president in 2012. For that to happen, Putin must choose someone loyal enough to cede supreme power. Small wonder that he seems to be keeping all his options open.