Putin critic Alexei Navalny thinks there's a 50/50 chance he'll be killed

Russia's main opposition figure thinks there's a 50 percent chance he will end up dead for speaking out against President Vladimir Putin, a fate that has befallen many of the Kremlin's enemies in recent years.

Alexei Navalny, 41, is Russia's most outspoken critic of the Putin regime, and is campaigning to challenge Putin in Russia's presidential election in 2018, even though he is officially barred from the ballot.

Correspondent Ryan Chilcote spent a week with Navalny for the second episode of "CBSN: On Assignment," ahead of mass protests in June against government corruption. Thousands of young people took to the streets in cities across Russia, with protesters marching through Moscow carrying signs that read "Navalny 2018" and chanting "Putin is a crook." More than 1,000 people were arrested, including Navalny, who spent 25 days in jail.

"Enemy of the State" airs in full on "CBSN: On Assignment" on Monday, Aug. 7, 2017, at 10 p.m. ET/PT on the CBS Television Network and on CBSN, the network's 24/7 streaming news service.

A lawyer by training, Navalny has been convicted three times over the past five years as his anti-corruption campaign has attracted the wrath of the Kremlin. Both he and his brother Oleg were convicted of embezzlement in 2014 and sentenced to 3.5 years in prison.

After widespread protests against the conviction, Alexei's sentence was suspended. Oleg, however, remains in prison.

Alexei said he "absolutely" feels responsible for Oleg's prison sentence, saying the Kremlin targeted Oleg to punish Alexei for speaking out against the regime.

"Well, it's 100 percent he's in jail just because he's my brother. It's the only reason," Navalny said.

As Navalny's notoriety has grown, the violence against him has increased in severity. Last year, he was attacked by a paramilitary group in southern Russia. This year, he was nearly blinded when someone threw a chemical dye in his face. He had to get surgery to save his eyesight.

Some of Putin's most vocal critics have ended up dead or in exile, although there is no direct evidence tying Putin to a series of mysterious deaths. Two years ago, Boris Nemtsov, an anti-Kremlin politician and ally of Navalny, was shot dead just outside the Kremlin.

Navalny said the chemical attack against him was the work of the regime.

"This attacker... was coordinated, and hired by government and administration of Putin. And we have a lot of evidence to that," Navalny said.

Asked about the odds he will end up in prison for his anti-corruption crusade, Navalny said, "Mr. Putin personal decides such things, and no one understands what is in his head."

Navalny had a more precise response when asked about the chances he ends up dead.

"Well, like, 50 percent I would be killed, or I would not be killed," he said.