By Dmitri Trenin

Moscow ― Westerners often see Russian politics in terms of a high-level struggle between liberals and conservatives: Ligachev and Yakovlev under Gorbachev; reformers and nationalists under Yeltsin; siloviki and economic liberals under Putin.

They also view Russia in terms of a tradition whereby every new tsar partly repudiates the legacy of his predecessor, creating a political thaw at the beginning of a new reign. Khrushchev's de-Stalinization is Exhibit A.

Both methods were used to describe the Putin-Medvedev relationship ― to understand its nature and dynamic, and what it portends for Russia. But observers remain puzzled.

To dismiss President Dmitry Medvedev as a mere Putin puppet, a constitutional bridge between Putin's second and third presidential terms, would be both unfair and wrong. Russia's third president has a broader role and a distinct function.

Conversely, portraying Putin as ``a man from the past," and Medvedev as ``a hope for the future," exaggerates the differences between them and omits the more important factors that unite them. A better analytical model is needed.

For all the apparent freshness of Medvedev's recent pronouncements, including his now famous article ``Go Russia!" ― which sounded a clarion call for modernization and liberalism ― he is borrowing massively from Putin's vocabulary of 2000.

This suggests that the issue of modernization, which lay dormant throughout the fat years of high oil prices, is back on the Kremlin agenda.

In 2008, Medvedev was installed in the Kremlin as part of ``Putin's plan," the substantive part of which was known as ``Strategy 2020," a blueprint for continued economic growth and diversification.

The intervening crisis only made the Kremlin modify and sharpen its plan. And Medvedev is a key agent in its execution.

Putin chose Medvedev carefully, and not only for his unquestionable loyalty, vitally important as that is. Putin, among other things, is a combative nationalist, and he wants Russia to succeed in a world of competing powers. He is certainly conservative, but he is also a self-described modernizer.

As such, he might be compared to Pyotr Stolypin, another conservative prime minister who famously asked for 20 years of peace and quiet ― mostly from liberals and revolutionaries ― to transform Russia.

Stolypin never got the chance ― a revolutionary assassinated him in 1911 ― and neither did Russia, which stumbled into World War I, leading directly to the collapse of the monarchy and the Bolshevik revolution.

Putin wants to finish the job, and much works in his favor. He is the tsar. He has both money ― the government's budget and the oligarchs' fortunes ― and the coercive power of the state firmly in his hand.

He is the arbiter at the top and the trouble-shooter in social conflicts below. His most precious resource is his personal popularity, which a flavor of consent to his authoritarian regime.

But none of that is good enough. The 75 percent of Russians who make up the Putin majority are essentially passive, and seek only the preservation of a paternalistic state. Putin can sit on their support, but cannot ride forward with it. The best and brightest are not there.

Enter Medvedev. His Internet-surfing, compassionate, and generally liberal image helps recruit a key constituency ― those beyond the reach of Putin himself ― to the Putin plan. Whether the plan succeeds is another matter.

Conservative modernization is a gamble. To modernize Russia, one must break the stranglehold of corruption, establish accountability, and free the media. At some point, Putin and Medvedev will have to decide.

Either they give priority to the survival of the current system and accept Russia's steady marginalization, or they start opening up the system, putting its survival at risk. Given the weight of geopolitical factors in Russian decision-making, it is difficult to foretell which path they will choose.

Putin is no King Lear. He understands leadership and control, and does not plan to retire. But Medvedev, today's front-office guy, is more of a junior partner than a simple salesperson.

He may yet grow in stature and influence, and eventually inherit the store. One thing is clear, though: he does not like raw meat and the taste of blood.

Thus, Putin's governing pact with Medvedev, his trademark creation, is likely to remain in force. Both members need each other.

So the real issue is not whether the noises that Putin and Medvedev make suggest real divergence, and a potential for rivalry, but whether there is daylight at the end of the tandem. Or, to put it differently, whether they choose modernization or marginalization.

Dmitri Trenin is director of the Carnegie Moscow Center. For more stories, visit Project Syndicate (www.project-syndicate.org).