WILLIAM BRANGHAM: In Russia today, it is rare to find someone who is willing to publicly criticize Russia's full-scale invasion of Ukraine, which is now nearing its third year.

But it's even rarer for that criticism to come from an elected official.

Nick Schifrin spoke with one Russian politician who decided to take a stand.

NICK SCHIFRIN: The day Sergei Medvedev decided his country was no longer his home, he traveled for four days through the snow, past the graffiti cursing the man he calls a monster to remove the blindfold he says Russians place over their own eyes.

SERGEI MEDVEDEV, Former Russian Lawmaker (through translator): All sane people can see what is happening right now.

After World War II, this is the largest ever war, a war where much has been sacrificed.

It's probably half-a-million deaths by now.

What's happening, it's awful.

NICK SCHIFRIN: Medvedev is not an activist.

He was a local lawmaker in Central Russia and member of the pro-government Communist Party.

But he says he could no longer sit in the same government waging war in Ukraine.

SERGEI MEDVEDEV (through translator): Whatever power I have, I will use it to stop this, because all politics right now in Russia are focused on justifications.

I don't see anything that can be justified.

Kharkiv, the bombing of Odesa, Bucha, I saw how cities were transformed into ruins.

I saw how they bombed theaters and children's day cares.

I saw this with my own eyes.

I have Internet access, as does every Russian.

Whoever wants to see sees.

NICK SCHIFRIN: On December 31, he posted unrestrained criticism of President Vladimir Putin.

SERGEI MEDVEDEV (through translator): May the creature who unleashed this bloody massacre die.

Deceived, maddened people, come to your senses.

Russia, wake up.

They're killing you.

I want to see Russia free from Putin's shackles.

NICK SCHIFRIN: Your post on December 31 went viral.

Why do you think it went viral?

SERGEI MEDVEDEV (through translator): People saw that they are not alone, because, in Russia, you can't speak freely about this.

Even though it was criticism, I reached the masses.

There were a lot of thanks.

By the way, there were more thanks than criticisms.

NICK SCHIFRIN: But he knew he had to flee.

He didn't feel safe using his credit card, so he left his home in Perm using a carpooling app to Yekaterinburg.

He then carpooled to Chelyabinsk and then to Kairak, where he crossed the Kazakh border on foot and hitchhiked to Karabalyk and then to Kostanay.

He bought a train ticket to Astana and flew first to the small Kazakh city of Aktau and then to Tbilisi, Georgia.

SERGEI MEDVEDEV (through translator): I was very nervous and very worried.

I'm not really afraid to go to jail.

I understood this could happen, but, in principle, I didn't want it.

NICK SCHIFRIN: Today's Russia punishes any and all criticism; 20,000 have been detained for protesting the war.

In November, Aleksandra Skochilenko was sentenced to seven years for replacing supermarket price tags with critiques of the war, including "Russian forces have destroyed over 20 medical centers in Ukraine."

It was Putin himself who two years ago launched a new wave of internal repression.

VLADIMIR PUTIN, Russian President (through translator): The Russian people will always be able to distinguish true patriots from scum and traitors and simply spit them out like a fly that accidentally flew into the mouth.

I am convinced that such a natural and necessary cleansing of society will only strengthen our country.

NICK SCHIFRIN: For his sins, Medvedev was kicked out of the Communist Party and the local parliament threw him out.

The vote was 33-0.

What is the current state of politics?

What is the current state of freedom of speech in Russia?

SERGEI MEDVEDEV (through translator): You cannot speak freely at all.

Everyone must speak for the war.

Any person who speaks out against will be repressed one way or another.

The regime worked the way it's supposed to work.

What's really going on?

Corruption, theft.

Everyone who is close to Parliament are thieves and corrupt.

NICK SCHIFRIN: Medvedev believes Russian society even goes beyond Britain's most famous critic of authoritarianism.

SERGEI MEDVEDEV (through translator): I think George Orwell himself could not have imagined that war would be renamed with an acronym.

He wrote about war and called war, war.

But in our country, they can't even call war a war.

It was called SVO, special military operation, and even the word war itself was banned.

NICK SCHIFRIN: What would happen to you if you returned to the Russian Federation?

SERGEI MEDVEDEV (through translator): Probably, I would have been arrested, like Alexey Navalny, like all the people who oppose Putin and the current war.

The war has changed people in Russia.

People are screaming slogans that even a decade ago they would have been afraid to express.

People send their sons and husbands to war and say that this is good.

NICK SCHIFRIN: It's a motherland that Medvedev no longer recognizes.

He's lost his home and job, but not his sense of purpose.

He will keep urging Russians to recognize reality.

As Orwell said, to see what is in front of one's nose needs constant struggle.

For the "PBS NewsHour," I'm Nick Schifrin.