On June 12th, thousands of protesters took to the streets of Moscow chanting "Putin is a crook" and "Russia without Putin!" The protesters, predominantly 16-27 year olds, flooded Tverskaya Street, a main artery leading to Red Square, waving Russian flags and holding signs that read "Navalny 2018." As a helicopter buzzed overhead, it didn't take long for riot police to move in, batons drawn.

By the end of the day, there were more than 1,000 arrests across Russia. The protests were inspired by a 41-year-old lawyer turned anti-corruption crusader named Alexei Navalny. He has announced plans to challenge Vladimir Putin in Russia's presidential election next March, but the Central Electoral Commission has suggested that an embezzlement conviction (which Navalny claims was politically prosecuted) may prevent him from running. Navalny hopes that by gathering enough support across the country, he can force the Kremlin to allow him to run.

"CBSN: On Assignment" spent a week with Alexei Navalny before the protests, in his Moscow office and on the campaign trail. "It's not about playing [a] game," Navalny told correspondent Ryan Chilcote. "It's not saying something or making rallies. We are really making this political work to win and without any doubts this corrupt regime will be crushed and another man will become president of Russia."

Unseating Putin will be a formidable challenge for the leader of the opposition movement, who has been effectively banned from Kremlin-controlled Russian state TV. As a result, Navalny has turned to the internet to spread his anti-corruption platform. His office is as much a production studio as a campaign office. It's oufitted with edit bays, audio booths, and a studio complete with cameras, lights and backdrops. The office is staffed by a few dozen employees, mostly millennials, working as programmers, designers, and editors who produce Navalny's weekly YouTube videos. For Navalny's supporters, this is what the revolution looks like.

While Putin is the primary target, Navalny's anti-corruption videos have alleged corruption in Putin's inner circle as well. "Corruption is something Mr. Putin chose as a foundation of his regime. It's an agreement between him and his allies in general of all officials in Russia." In March, Navalny posted a video online in which he accused Russian Prime Minister Dmitry Medvedev of widespread corruption, accepting bribes in the form of an $85 million mansion. The video inspired tens of thousands of demonstrators to take to the streets in cities across Russia.

"I'm just connecting dots," Navalny said. "It's obvious for everyone that this low level of life. This poor quality of life is connected with the corruption. Everyone in the country understands it, but I am saying it publicly."

The Kremlin's response to Navalny's accusations is to say little, if anything, about them, or him. No government official would speak with us about Navalny. But during the G-20 Summit this summer, correspondent Ryan Chilcote asked President Putin about his thoughts on Navalny, and why he never referred to Navalny by name. "I think we can have a dialogue with people who offer a constructive agenda," Putin responded. "But if we're talking about just attracting attention to yourself, that's not interesting for dialogue."

Challenging the Kremlin with accusations of corruption comes with significant risks. In April, Navalny was nearly blinded when someone threw a chemical dye in his face. He flew to Spain to get emergency surgery to save his eyesight and was forced to wear an eye patch for several weeks. When asked about the challenges of being an opposition figure in Russia, Navalny was stark about his odds: "50% I would be killed or I won't be killed."

While there has been no direct evidence of Kremlin involvement in interference with opposition figures, some of Putin's most vocal critics including political opponents, human rights lawyers and journalists have been attacked, murdered, or gone into exile. In 2006, Alexander Litvenenko, a Russian FSB agent-turned-Kremlin critic was poisoned with the radioactive isotope Polonium 210. That same year, the journalist Anna Politkovskaya, was shot dead. And in 2015 Boris Nemtsov, an anti-Kremlin politician, was assassinated on the Bolshoy Moskvoretsky Bridge outside the Kremlin.

Mikhail Khodorkovsky knows that risk well. He was once Russia's richest man until he used his fortune to fund opposition parties. He spent 10 years in prison on what he says were politically-motivated charges, and now lives in exile in London. Khodorkovsky told CBS News he does not believe Navalny will be assassinated because of the notoriety that would bring him and his cause. Still, he said there is little Navalny can do to prevent that from happening. "It's like walking through construction site with bricks falling from up above. A brick might strike you, it might not strike you. The only choice you have is whether to walk through this construction site or not. Navalny can't influence this situation."

To build that future as the president of Russia, Navalny needs to convert his base of online followers into real support on the ground. To make that happen, Navalny has spent much of this year opening campaign offices across Russia. His pitch is simple: the salaries of most Russians are low, while those with connections to the government enrich themselves through corruption. His campaign rallies would be familiar to western voters, but they are a novelty in Russia, where Navalny's team sometimes faces harassment from the local police and can have difficulty finding someone to rent them space for a campaign rally.

For months, Navalny rallied his supporters to protest on June 12th, a national holiday celebrating the creation of the modern Russian state. When Navalny was issued a permit for the demonstration outside Moscow's city center, he called on his supporters to march there anyway, defying the local government, and along with it, the Kremlin. In an effort to head off a mass demonstration, Navalny was arrested outside his home the morning of the protests. When thousands of his supporters demonstrated anyway, riot police quickly moved in. Over the course of several hours, they arrested more than 700 demonstrators before finally clearing the street and ending the demonstration.

Before Navalny's arrest, CBS News asked him why he continues to do this work despite the government harassment, attacks, and imprisonment. "Because I believe that Russia can have a better life," he said.

Alexei Navalny was released from detainment last month. He is already planning more demonstrations against the government.