In power for nearly a quarter century, Vladimir Putin, 71, is a modern-day tsar -- an autocrat largely unaccountable to his people -- except he has no known successor. Whether the Russian president rules for another week or another decade, there will come a time when he's gone. Who might replace him is a mystery. Also unclear is how Putin might be replaced: by a violent coup? Some legal way under the Russian constitution? In this episode, Liana Fix of the Council on Foreign Relations and Maria Snegovaya of the Center for Strategic & International Studies use the Soviet past as a guide to understanding possible scenarios under which a successor may emerge -- and what new leadership in the Kremlin means for Russia, Europe, and the United States.