Thousands of people took to the streets from Moscow to Vladivostok on Sunday to protest in the biggest mass demonstrations in five years. Many heeded the call of opposition figure Alexei Navalny, who levied corruption charges against Prime Minister Dmitry Medvedev in a video. Many of the protests, including those in Moscow, were not officially sanctioned, leading to hundreds of arrests, including Navalny's. A Moscow court sentenced him to 15 days' jail time and a fine of 300 euros ($326).

The weekend protests were the next chapter following those from May 2012, when Vladimir Putin was set to begin his third term as president. The mostly peaceful movement escalated over several months. Many protesters were arrested and sentenced to prison terms, frustrating the opposition's momentum.

The man behind the protests

Presidential elections are coming up in 2018, with Putin expected to run again. Navalny, who spawned the last round of anti-Putin protests, has signaled his desire to run as well. It remains unclear if he will be allowed - due to a court ruling against him in February in a financial crimes case. The case is under appeal in Russia's courts, but Navalny is looking to the European Court of Human Rights in Strasbourg for help outside of the sphere of Russian state influence.

The 40-year-old made a name for himself as a blogger fighting against corruption. Early on, he faced criticism for what some called an overly nationalistic tone.

He went on to receive a quarter of all votes cast in a 2013 Moscow mayoral election.

Target: Medvedev

Navalny made headlines by accusing state leaders of corruption. "Corruption has the public simmering. It is the most important political issue," he told DW in 2016, though admitted it was difficult to mobilize the Russian people against it.

His documentaries about corruption seem now to have hit a nerve. His latest about Medvedev's alleged corruption has received 12 million views. In the film, he claims Medvedev used a network of foundations to secretly buy up mansions, vineyards and yachts. Medvedev's spokesman called the film just part of the election campaign.

Despite the noise, 10 percent of surveyed voters have said they would support Navalny in the presidential election, according to the internationally respected Levada Center. Putin's support remains at 80 percent.

Students against Putin

Although many in Russia are puzzled by Navalny's success in mustering relatively large anti-government support, some students are rallying behind the Kremlin critic. An arrest of a student a few days ago in Bryansk, a city south of Moscow, caused a stir. A secretly-made recording of a conversation between the school's principal and the class went viral on social media. In it, a student is heard to say he is against Putin and Medvedev's United Russia party not because it has made Russia worse, but because the party has been in power for too long.

Many of the young people who participated in the weekend protests have only known Putin in power, Russian journalist Oleg Kashin told DW. "Putin would still bother them," he said, if only for how long he has been around.

Thaw in sight?

Overshadowed by Navalny's film and the subsequent protests was another surprise: Communists in the Duma, an opposition party in name only that tends to follow Kremlin wishes, want the corruption allegations investigated. The rare call for a sitting Russian leader to be held accountable has fueled speculation that Putin is looking to sack Medvedev, with some experts suggesting he would succeed the sitting president and bring about more liberal policy - much as Nikita Khrushchev did during the Cold War.

Opposition circles in Russia have been talking for weeks about a potential political thaw, based on a few mild rulings handed down by an otherwise stringent judiciary seeing to the release of certain activists and Kremlin critics. Sunday's protest arrests will put the thaw theory to the test, Kashin said, while Navalny continues a fervent game of politics.