Boris Nemtsov killing: Who is left to challenge Vladimir Putin?

The assassination ofBorisNemtsovmay havedealt a severe blow to theopposition movement in Russia, but it's a group that was alreadyseverely marginalized, with no one figure able to garner enough support to offer any realthreat to President Vladimir Putin'shold on power.

Nemtsovwas shot in the back four times on Friday. Hisfuneral on Tuesday drew thousands of Russians to pay their respects, and he was arguably the most prominent opposition figure to be slain in Russia during Putin's 15-year rule.

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But even Nemtsov, a former deputy prime minister, had little power and almost no influence,saidRandall Hansen, director of the University of Toronto's Centre for European, Russian and Eurasian Studies.

And his death, the most recent killing of a high-profilecriticof theKremlin,"ina horrible literal sense has reduced [the opposition leaders']numbers but also massivelycreated insecurity, fear andintimidation among them," Hansen said.

"There's two types of opposition. There's the opposition of the street, and the opposition of the organized liberalpolitical elite. And in a sense they've both been decimated," Hansen said.

"I think the opposition is not particularly well-mobilized, which isnot its fault," addedLucanWay, a University of Toronto associateprofessor of politicalscience whofocuseson democratic transitions and the evolution of authoritarian rule in the former Soviet Union. "You dont get the sense that it has a real game plan. Its more just waiting for acrisis to happen."

Instead, opposition leaders seem tohave a "dissident mentality," Way said, suggestingthat they're sofar from gaining power they can say things that are unpopular, like speaking out against the war in Ukraine.

"Youonly do that if you haveno chance," he said.

Outspoken foes detained, or not in Russia

Meanwhile, despite a sharp slide in therubleand international sanctions over the Ukraine crisis, Putin continues to enjoy public support while the opposition faces repeated threats of detention, arrests and violence.

There arestill, however, prominent leading opposition figures who remainoutspoken opponentsof Putin's policies.

MikhailKasyanov: Hewas Russias prime minister from 2000 to 2004, during Putins first term as president, but has sincesince become anoutspoken critic and leading figure in the opposition movement, buoyed by his past political credentials.

He's a bit likeNemtsovin that he's quite brave incarrying on thefight, but there'srelativelylittle support," Hansen said.

Alexei Navalny: The Russian lawyer and bloggerhas garnered a lot of support and recognition through his website, which hasexposed a series of corrupt dealings.But Navalnyand his brother were both charged and convicted of embezzlement (charges they both deny). Navalnyiscurrently under house arrest.

MikhailKhodorkovsky: The former oil tycoon spent 10 years in prison on charges of evading taxes, stealing oil and laundering the proceeds.He was later pardoned by Putin and currently lives in Switzerland. Hefounded Open Russia, an online forum dedicated to democratic reform in Russia.

Although Khodorkovskyinitiallysuggested he had no political aspirations, he has, as the New York Times reported,"positioned himself as the leader of a renewed opposition intent on replacing Mr. Putin and bringing European-style democracy to Russia."

GarryKasparov:The former world chess champion has become an outspoken critic of Putin, comparing his regime to the rule of Adolf Hitler. Kasparovhas been detained and arrested at different anti-Putinrallies. But he currently lives in New York, fearing that if he were to return to Moscow he could be arrested on a trumped-up charge.

"A lot of people are afraid to return to the country.Khodorkovskyis one ofthem. Kasparov is another," said David Satter, author andformer Moscow correspondent who was expelled by Russia. "So it'shardtosaywhat they can do from outsidethe country."

Way expressedskepticismthat any of the currentleading oppositionfigures would be able to attract the support needed to topple Putin,believing instead that only a defector from within the ranks of the president's cabinet would have a chance.

'Nationalist credentials' neededto win

"It's hard to imagine a Russianoppositionleader without good Russian nationalist credentials.I think to win you need the insiderconnections and the Russiannationalistcredentials toreally challenge Putin," he said.

As well,Satter said that Russia is very unpredictable, and whilethe opposition as a whole doesn't currently have much support, the situation could change.

"It doesn't have the ability to bring a lotofpeople out into the street. It's beingharassedand thepublicright now giveseverysign of supporting the [Ukraine] war, but this is notnecessarilya permanentsituation," he said.

"It'sanextremelymanipulatedenvironmentand conditionscouldchangeifthere's an economic collapse, amilitarydefeatin Ukraine. There are anynumberofthings that couldhappenthatcouldchangethewholesituation."