A few weeks after Chelsea Manning was released from military prison, having served seven years of a 35-year sentence for leaking official secrets, she came to a terrible realization. “I was out, but I saw that while I had been away, the prison had moved out here as well. That’s how I feel. I feel like I haven’t left, we’ve just exchanged prisons.”

That grim assessment, that even in freedom she was trapped within a prison, dawned on her as she walking one day through the streets of Brooklyn. The New York borough has a reputation for hipster cool, but she was shocked to see so many heavily armed police.

“There was this immense police presence and they were militarized. I’ve been part of an occupying force in a foreign country, and I know what that looks like. That’s what I saw in Brooklyn – an occupying force.”

Her powerful fear about what America has become in the seven years of her incarceration, combined with an equally powerful determination to do something about it lies behind Chelsea Manning’s announcement this week that she is running for a US Senate seat.

Fear and determination – you could say that has been her dual hallmark since she made the fateful decision in 2010 to leak a vast trove of 700,000 secret documents when she was working as an intelligence analyst at a US military base in Iraq.

In the first interview Manning, 30, has given since she posted details of her Senate bid on Twitter, the Guardian asked her whether she drew a straight line between becoming one of the most famous – and most severely punished – official leakers in US history and her political ambitions today. “It’s certainly not a direct line,” she said. “It’s windy, a lot has happened. I’m a very different person than I was 10 years ago.”

People want to shut dissent down. We have to push back. I’m not going to be deterred by someone saying horrible things

But there are certainly parallels between the two events. It was an act of extreme courage – some would, and did, say folly – to download and transmit war logs, embassy cables, videos and Guantánamo files to WikiLeaks. It is an act of extreme courage – some might, and are, saying folly – to run for the US Senate.

There’s also a profound dichotomy to be found somewhere along that winding road between her May 2010 arrest and her new campaign: she wouldn’t have the global platform she enjoys today were it not for the at times brutal treatment she received at the hands of the US military. How does she make sense of such opposites?

“I haven’t made sense of it,” she said. “And I don’t think there has to be an explanation. I learned very quickly that my experience in prison has shaped my understanding of the world.”

We meet, appropriately on the first anniversary of President Obama’s commutation of Manning’s sentence, in her apartment outside Washington DC. It has a large living room that is full of light, but strangely empty and devoid of human touch, as though she had replicated, albeit more comfortably, the spartan aesthetic of a prison cell. The walls are almost bare besides prints of Oscar Wilde and anarchist Emma Goldman above the fireplace, and a copy of Manning’s commutation letter.

She is dressed in black, as she was in the video launching the Senate campaign in which she carried a red rose as symbol of political resistance. In the bright light of the room, her eyes are piercingly blue-grey, topped by a slash of pink eye shadow. She wears a silver necklace with a hashtag pendant; asked why, she replies without hesitation: “Twitter … got me out of prison.”

To say that Manning has taken on a tough job running for office in her home state of Maryland is an understatement. The incumbent in the 26 June Democratic primary, Ben Cardin, is a seasoned veteran going for a third term, the leading Democrat on the Senate foreign relations committee, with a large and loyal following of centrist voters.

Facebook Twitter Pinterest Chelsea Manning talks to Ed Pilkington in her apartment outside Washington. Photograph: Tracey Salazar/The Guardian

Cardin is reported to have at least $2m in his war chest, and the last time he faced a primary challenge in 2012 he beat his opponent by 74% to 16%. Manning has raised a little under $50,000 so far, drawn from small online donations, with a staff currently of two that she wants to keep lean throughout the campaign at under 10.

How can she possibly compete?

“We know it’s a real fight ahead of us,” she said, insisting that she is in the race to win. Whatever happens, though, she will not compromise her convictions to garner votes. “We do want to win, but if we lose our principles then winning wouldn’t matter.”

Manning says she is putting her faith in victory in the local activist and student groups with whom she has been building connections since her release. “We are not doing a centralized ground game, we are waiting for local communities to come to us. I will come, and I will listen.”

Does she fear that she could crash and burn, as the Black Lives Matter celebrity DeRay Mckesson did when he contested the Democratic primary for Baltimore mayor in 2016, coming in sixth with just 2% of the vote?

“Baltimore is a deep-rooted city with a very active activist community, and I don’t think DeRay utilized that,” she replied. “I’m not going to criticize a friend of mine, but at the same time we are talking to local people in Maryland, and we are taking the time.”

‘This is my moment’

Manning’s political style is already fully on view through her Twitter feed. It is vibrant and provocative, fusing upbeat jingles like “#WeGotThis” – a mantra that she developed in prison to buoy up her spirits at times of despair – with blunt language that compares the federal immigration agency Ice to the Gestapo and says “fuck the police” without elucidation.

That approach clearly works for her 323,000 Twitter followers. But how it will play on the doorsteps of Maryland, a state with a large federal employee contingent (the NSA spy center is based here), remains to be seen.

Manning calls her politics “radical anti-authoritarianism”. Asked to explain, she grew animated, her voice crescendoing: “The United States has the largest and most expensive military in the world, but we always want more. We have the largest prison system in the world, yet we want more. We have the largest and most sophisticated intelligence apparatus in the world by far, and still we want more. How much is enough? That is my moment – we need this to stop.”

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Though she says she has no animus towards Cardin – “I voted for him twice” – she sees him as part of the problem. She points to the Israeli Anti-Boycott Act that he championed that has been widely criticized for attempting to stifle protests against Israeli settlements.

In her first campaign statement, Manning mentions three core policy areas: criminal justice, healthcare and immigration. In each, she pitches herself strikingly to the left of Bernie Sanders. Prisons should be closed and inmates released; all hospitals should be free at the point of use, no questions asked; US borders should be open.

And she really means open. “We shouldn’t be denying the absolute right to come into the United States. You have a right, everybody does.”

What would she say to a Maryland voter worried about terrorists entering the country? “We have domestic terrorists and they can travel wherever they want. Closing off the borders doesn’t solve the problem.”

That initial position statement is as interesting for what it omits as for what it addresses. Manning is silent on transgender politics, despite being at the forefront herself of the trans movement. And she does not mention Donald Trump.

Why no reference to the man who for many progressives has become the embodiment of evil?

“All our problems are personalized into one individual, but it’s a systemic problem. Our broken immigration system didn’t pop up overnight, it was a machine built over decades by centrists from both sides.”

Manning said that she will soon begin appearing in public meetings at the invitation of local groups. Given that her Twitter feed regularly attracts vile hate-filled comments and threats of violence towards her from transphobic and rightwing detractors, is she not anxious about her safety?

Facebook Twitter Pinterest Marchers at San Francisco pride call for Chelsea Manning’s release in June 2015. Photograph: Elijah Nouvelage/Reuters

“It doesn’t bother me. These people want to shut dissent down, and we have to push back. I’m not going to be deterred by somebody saying horrible things to me.”

Attack lines that she is certain to face on the campaign trail have already begun to be aired. She is a traitor to her country, is the most predictable iteration, followed by conspiracy theories that she is in the pay of the Russians attempting to destabilize a sitting Democratic senator.

Again she appears unfazed. “Everybody is a traitor these days. James Comey, Hillary Clinton, Trump, Obama … the word has no meaning any more. Any form of ‘I don’t agree with you’ becomes ‘treason’, and in that kind of society we can’t have debates.”

WikiLeaks and its founder, Julian Assange, to whom she leaked the documents in 2010, are also certain to be invoked against her. What does she say now of WikiLeaks?

“I made a decision in 2010 to release the documents. I reached out to the New York Times and the Washington Post, I ran out of time, and that was the decision I made. I can’t change that.”

Has she had any contact with Assange since the data transfer?

“No. Zero.”

Perhaps the most serious charge so far has come from the right. The Conservative Review wrote that the Manning v Cardin battle “benefits the Republican party tremendously. It will pit the Democrat party’s establishment wing against the radical identity politics of its more progressive members.”

How does she answer that theory that by injecting “radical anti-authoritarianism” into the race, she could have a reverse impact by presenting a gift to radical reactionaries?

Manning’s answer is that in this fevered age all political bets are off. “Pundits say all kinds of things, and they are always wrong. Remember election night 2016? Times are different. People are upset. The political system we have isn’t representing people any more. So yeah, we need a fight.”

To that fight Chelsea Manning, one-time homeless person, US soldier, official leaker, military prisoner, now Twitter celebrity and trans woman, is joined. Let the wild rumpus begin.