The assassination of Boris Nemtsov may have dealt a severe blow to the opposition movement in Russia, but it's a group that was already severely marginalized, with no one figure able to garner enough support to offer any real threat to President Vladimir Putin's hold on power.

Nemtsov was shot in the back four times on Friday. His funeral 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. 

But even Nemtsov, a former deputy prime minister, had little power and almost no influence, said Randall 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-profile critic of the Kremlin, "in a horrible literal sense has reduced [the opposition leaders'] numbers but also massively created insecurity, fear and intimidation among them," Hansen said. 

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

"I think the opposition is not particularly well-mobilized, which is not its fault," added Lucan Way, a University of Toronto associate professor of political science who focuses on democratic transitions and the evolution of authoritarian rule in the former Soviet Union. "You don’t get the sense that it has a real game plan. It’s more just waiting for a crisis to happen." 

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

"You only do that if you have no chance," he said. 

Outspoken foes detained, or not in Russia

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

There are still, however, prominent leading opposition figures who remain outspoken opponents of Putin's policies.

Mikhail Kasyanov: He was Russia’s prime minister from 2000 to 2004, during Putin’s first term as president, but has since since become an outspoken critic and leading figure in the opposition movement, buoyed by his past political credentials.

“He's a bit like Nemtsov in that he's quite brave in carrying on the fight, but there's relatively little support," Hansen said.

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

Mikhail Khodorkovsky: 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. He founded Open Russia, an online forum dedicated to democratic reform in Russia.

Although Khodorkovsky initially suggested 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."

Garry Kasparov: The former world chess champion has become an outspoken critic of Putin, comparing his regime to the rule of Adolf Hitler. Kasparov has been detained and arrested at different anti-Putin rallies. 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. 

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Mikhail Khodorkovsky is among the remaining leading opposition figures of Russian President Vladimir Putin's regime. (Yves Logghe/Associated Press)

"A lot of people are afraid to return to the country. Khodorkovsky is one of them. Kasparov is another," said David Satter, author and former Moscow correspondent who was expelled by Russia. "So it's hard to say what they can do from outside the country."

Way expressed skepticism that any of the current leading opposition figures 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' needed to win

"It's hard to imagine a Russian opposition leader without good Russian nationalist credentials. I think to win you need the insider connections and the Russian nationalist credentials to really challenge Putin," he said.

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

"It doesn't have the ability to bring a lot of people out into the street. It's being harassed and the public right now gives every sign of supporting the [Ukraine] war, but this is not necessarily a permanent situation," he said. 

"It's an extremely manipulated environment and conditions could change if there's an economic collapse, a military defeat in Ukraine. There are any number of things that could happen that could change the whole situation." 

With files from The Associated Press and Reuters