Medvedev is a political nobuddy who was endorsed by Putin and backed by the in-power United Russia party. The top "comepitors" include the pro-Kremlin, pro-Putin, pro-Glory Days Communist Party, the pro-Kremlin, pro-Putin, very scarily anti-West while still named the innocent Liberal Democratic Party, and the pro-West token Democratic Party of Russia. Parties such as Another Russia and others had little chance at stopping Putin's machine but were barred anyways.
Putin has promised the people that he will stay on as hopefully the Premier (prime minister). Right now Russia's system has the president as the most powerful spot but Putin is likely to control things either through reform or behind the scenes. Medvedev will continue Putin's policies of having Russia being a stick in the eye against American plans.
The reason Putin allowed the elections is to have the junta system look democratic. It is interesting to note; however, that this is the first time a Russian leader has voluenteraly transfered power without resigning, dying, or being forced out since the rise of the Tsars over 500 years ago!