Update below the fold–Ivanov is not the new PM.

Reuters is reporting that Russian Prime Minister Mikhail Fradkov has stepped down. No replacement has yet been named, though Vedomosti is reporting that First Deputy Prime Minister Sergei Ivanov is the most likely candidate.

Prime ministers may come and go, but this is big news because of the open question: who will be the next president of Russia. While I wouldn’t be entirely shocked if there was a sudden domestic crisis that necessitated a third term from Vladimir Putin, most Russia watchers believe that he wants to hand off the open reins of power to someone else. The presidential election is only six months away, and Putin still hasn’t designated his preferred successor.

Ivanov’s star is already perceived to be on the rise: earlier this year he was relieved of his position as Defense Minister, which was becoming tainted by scandals related to brutal hazing of recruits, and promoted to the position of first deputy prime minister, at an equal level with Dmitri Medvedev, who is widely perceived as Ivanov’s main rival in the behind-the-scenes presidential race. If Ivanov is indeed named the new prime minister, it will be a powerful signal: Putin himself was named prime minister during the waning months of the Yeltsin administration.

Update: Vedomosti was wrong–the new PM is Viktor Zubkov. More later once I’ve had a chance to read up on him. Zubkov is surprising to just about everyone. Putin certainly does love to keep everyone guessing. In the meantime, there are some interesting comments from Dmitri Trenin, of the Carnegie Moscow Center, via FP’s Passport blog.