For more than a year, the conventional wisdom had been that two candidates -- First Deputy Prime Ministers Sergei Ivanov and Dmitry Medvedev -- were vying to be Vladimir Putin's anointed successor as president.
But speaking at a briefing on Russian-U.S. relations earlier this summer, Shuvalov suggested that Putin might have a surprise in the works.
"People talk about these two candidates, possible candidates," Shuvalov said. "But you know my president could create another surprise and, you know, maybe even later during this year you will know about another possible figure."
Shuvalov's comments set off a wave of speculation in Moscow and elsewhere about the identity of the mysterious figure who could become Russia's next leader.
It was eight years ago this week that Vladimir Putin burst out of obscurity on to the Russian political scene. Putin was the ultimate dark horse candidate when then President Boris Yeltsin anointed the dour former KGB officer as his chosen successor on August 9, 1999.
And many in Moscow are beginning to wonder if a surprise candidate might emerge this time as well.
'The Third Man'
So who is this "third man," as some media have come to call the mystery candidate? Some of the early chatter has focused on a woman: St. Petersburg Governor Valentina Matviyenko.
Analysts say that Matviyenko, who is fiercely loyal to Putin, is the ideal candidate for the so-called "caretaker president" scenario. According to this scenario, a weak president would be put in office and Putin would continue to de facto rule Russia from behind the scenes after leaving the Kremlin.
"For such a plan she [Matviyenko] is an ideal figure. She doesn't have her own ambitions and is 100 percent oriented to Vladimir Putin," Andrei Ryabov, a political analyst with the Moscow Carnegie Center, says.
Ryabov and other analysts say that as governor of St. Petersburg, Matviyenko also has demonstrated one of the key qualities Putin is looking for in a successor: the ability to balance the interests of the various clans that make up Russia's ruling elite.
"We know that the current elite is from St. Petersburg, they all had some kind of interests there. Valentina Matviyenko was the kind of politician who was able to balance their interests on their home turf [in St. Petersburg]. She has wide contacts with very different [political and commercial] circles," Ryabov says.
The Russian Constitution forbids Putin from serving two consecutive terms -- but it does not forbid him from returning to power after another president has been in office.
Many analysts say Matviyenko is the perfect candidate to hold the Kremlin until Putin returns.
"If they make her president temporarily, under the condition that she must resign in a year or two, she will most likely not betray them if they want to make Putin president again. In this way, Matviyenko is comfortable," says Vladimir Pribyulovsky of the Moscow-based Panorama think tank.
Matviyenko has repeatedly said she will not run. In a July 23 interview with the "Izvestia" daily, she said she does not "suffer from megalomania or presidential ambitions."
Strong Chief Executives
Moreover, analysts point out that the caretaker president model is unlikely to work in Russia, with its tradition of strong overbearing chief executives.
"I hardly think this is a realistic scenario because a technical president for a country that is not accustomed to strong parliamentary institutions is strictly hypothetical," Ryabov says.
If Matvienko fits the scenario in which Putin will try to install a weak president, Vladimir Yakunin, head of the state-run Russian Railways company, represents the opposite -- a potentially strong president in the Putin mold who would continue the current Kremlin leader's policies.
"First of all [Yakunin] is a well-connected person. Second, he has serious money, not only from railways but from many other businesses," Ryabov says. "He has contacts with different parts of [Putin's] Petersburg team, including the so-called Chekist businesspeople," Ryabov adds, using the Russian slang expression for security officials who are engaged in business.
Railways head Vladimir Yakunin (TASS)
As head of Russian Railways, Yakunin leads Russia's largest company after Gazprom. He is close to Putin. His dacha, or country residence, is next door to the president's, and the Russian media made much of the fact that during Orthodox Easter services, Yakunin was at Putin's side.
But Yakunin's strengths are also his main weaknesses.
"He is able to find agreement among various interests but, unlike Matviyenko, he will not be a puppet," Pribylovsky says.
Yakunin's business interests, as Russian Railways chief, clash with those of Putin's powerful deputy chief of staff, Igor Sechin, who is on the board of directors of the oil giant Rosneft.
"He is without a doubt serious and tough, but he is unacceptable to many from the Petersburg team. And because of this his chances are very small," Ryabov says. "Putin's task is to find the person who is acceptable, if not for everybody [in the St. Petersburg elite], at least for the majority."
The true dark horse, the rising star that many Kremlin watchers have theirs eyes on right now is Sergei Naryshkin, who Putin named deputy prime minister responsible for foreign economic relations in February.
Ryabov says Naryshkin's star is clearly rising.
"On the one hand, he has earned a lot of trust," Ryabov says. "He has worked on gas transport from Turkmenistan, which is very important. It wasn't in the public eye, but it was very important. He has worked on economic ties with the countries of the CIS, which is also very important but doesn't get much publicity. Obviously being assigned such tasks speaks to the large degree of trust he enjoys at the top."
Other dark-horse candidates mentioned by analysts and in media reports include Sergei Chemezov, head of the Russian arms export company Rosoboroneksport; Krasnodar Governor Aleksandr Tkachev; Krasnoyarsk Governor Aleksandr Kholoponin; and Putin's envoy to the North Caucasus, Dmitry Kozak.
Kremlin watchers say Putin's goal is to keep the current elite -- the so-called "St. Petersburg team -- in place after he departs the Kremlin.
In addition to loyalty to Putin and his political line, any candidate must therefore also be acceptable to the various clans that make up Putin's inner circle.
"There are two factors: the collective Putin and the individual Putin," Pribylovsky says. "They are more or less equal [in strength]. I don't think Putin can name someone that his circle is suspicious of. Moreover, he wants to maintain the status quo. But they [the inner circle] also cannot force anyone on him."
Pribylovsky, Ryabov and other analysts say the key differences among the clans are not ideological, but rather a desire to protect their commercial interests and political positions.
"You can think of it like a closed corporation in which Putin has 50 percent of the shares and the remaining 50 percent of the shares are distributed among about 10 or 15 people [who make up Putin's inner circle]," Pribylovsky says.
Despite the so-called "third man" scenario and the emergence of so many dark horse candidates, many analysts say they still see Ivanov and Medvedev as the frontrunners. That impression was strengthened when both made high-profile appearances at the Kremlin-backed youth group Nashi's summer camp in July.
Most Kremlin watchers expect Putin to announce his chosen successor soon, probably sometime in the fall. After all, it was eight years ago this week when Yeltsin shocked Russia -- and the world -- by naming the then-obscure Putin as his chosen heir.