Dmitry Medvedev's endorsement as presidential candidate by four pro-Putin political parties and by Vladimir Putin himself ends months of guessing games. Mr. Medvedev's appeal to Mr. Putin to serve as prime minister not only confirms Mr. Putin will play a pivotal role in Russian politics after he steps down - it signals that Mr. Putin, not Mr. Medvedev, will remain the No. 1 politician in Russia for years to come.

If Mr. Putin agrees to serve, it is most likely he will be a super-prime minister, the "national leader" with responsibilities over foreign, security and defense policy. It is possible that after the March elections Mr. Medvedev will change the constitution or promulgate laws transferring control of some or all of these areas to Mr. Putin.

Russia fundamentally differs from Mexico, which in the last century was under the rule of the Institutional Revolutionary Party (PRI) for 70 years. There, an outgoing president selected a successor, who then kept the former president safe. However, in Mexico, ex-presidents did not play an active role in government.

In the meeting with Mr. Putin I attended this past September in his Black Sea residence Sochi, he expressed hope he would continue to influence public affairs in Russia. "My successor will have to negotiate with me how we divide power," Mr. Putin said. Soon after, it became known Mr. Putin might become Russia's next prime minister.

Mr. Medvedev, media shy, is always keen to speak the language Westerners understand, hailing property rights, robust private sector, transparency and fighting corruption. He sounds serious and sincere.

However, as Mr. Putin will remain in the driver's seat, the chances for massive liberalization in strategic sectors, such as energy, remain meager. The Russian oligarchs, who are tight with top politicians, do not favor economic openness, which only breeds competition. Mr. Putin expressed his views in his Ph.D. dissertation, which hails the role of giant Russian state-owned natural resources companies in the global economy. Only the economic failure of such corporations could possibly force Mr. Putin and Mr. Medvedev to reconsider their statist approach.

Mr. Medvedev, a Putin protege, is perceived as a weak bureaucratic player and will require Prime Minister Putin's support as he consolidates power in the brutal world of Russia's political and oligarchic struggles.

In contrast to the judo black belt of Mr. Putin and other KGB veterans, Medvedev, a professor's son and a law professor himself, is soft-spoken and bookish. Having focused on domestic politics and policy, he lacks experience in foreign policy and national security and may depend on Mr. Putin's advice and support in these areas. He already has been called a "socially oriented president."

Despite his reputation as a market supporter, Mr. Medvedev is unlikely to be able to implement a classic liberal economic policy that can lead to more foreign investment and competition.

First, there are promises to keep, especially to the siloviki group - secret service generals who also control some of the choicest morsels of the economy. Kremlin Deputy Chief of Staff Igor Sechin leads this faction and also is chairman of Rosneft, the largest Russian state-owned oil company.

The siloviki have recently taken a bit of a beating. The public fight between the Federal Security Service, headed by Sechin ally Nikolay Patrushev, and the Federal Anti-narcotics Service led by Putin ally Gen. Viktor Cherkesov, spilled into public view with Gen. Cherkesov penning a controversial op-ed in Kommersant, blasting his FSB competitors.

Mr. Putin also did not appreciate a recent Kommersant interview with Oleg Shvartzman, essentially a business manager for the Sechin-affiliated business group. He disclosed too many details about the inner workings of the group's Kremlin-affiliated Russian business for anyone's comfort, including offshore tax evasion and extortion by power elites. While these publications may have weakened the siloviki, their power is still immense, and Mr. Putin and Mr. Medvedev must take their interests into account.

Mr. Medvedev, lacking a KGB, military or other security background, needs to keep the siloviki appeased and may have a hard time getting control of the levers of power. He will need Mr. Putin's continued support.

Even if Mr. Medvedev ever stands on his own two feet, he must remember the Russian public, from the days of the Romanovs and the Soviet Union, has always been unenthusiastic, to say the least, about weak leaders: Nicholas II, Josef Stalin's heir Georgii Malenkov, Nikita Khruschchev, Mikhail Gorbachev and Boris Yeltsin are all viewed with disdain by the majority of Russians, while many have a positive view of "strong leaders" such as Peter the Great, Catherine the Great, Alexander II, Mr. Putin and even the monstrous Stalin and bumbling Leonid Brezhnev.

Mr. Medvedev's greatest long-term threat is his perceived weakness. Historically, each regime in Russia has been markedly different from its predecessor. Thus, Mr. Gorbachev's reign differed from Mr. Brezhnev's, Mr. Yeltsin's administration differed from Mr. Gorbachev's, and Mr. Putin's rule was unlike Mr. Yeltsin's. Messrs. Gorbachev, Yeltsin and Putin all "campaigned" as the antithesis of their predecessors. Mr. Medvedev, on the other hand, is Mr. Putin's "official" heir and will find it impossible to shed his boss' control and vision even if he wants to.

Nevertheless, to succeed, Mr. Medvedev will eventually need to show his mettle, both in charting his own policy and by winning in power politics.

Ariel Cohen is senior research fellow at the Heritage Foundation and senior adviser to the U.S.-Ukraine Business Council.