(r-l)President of Russian Railroad Vladimir Yakunin , Head of presidential administration Sergei Sobyanin , Russian PM Mikahil Fradkov , President Vladimir Putin during the Easter church service in Moscow. The main candidate for russian presidency First Deputy Prime Minister Dmitri Medvedev announced on Thursday, Dec. 20, 2007 that Kremlin chief of staff Sergei Sobyanin (pictured) would head his presidential campaign.