Since Theresa May announced her call for a general election yesterday, thousands of people have joined the Labour party – not just because they are disgusted at what the Tories are doing to our society, but because they know that this election is a unique opportunity. For the first time in many of our lives, we have a Labour party that is committed to ending austerity and bringing about the structural change necessary to fundamentally rebalance wealth and power in Britain.

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These policies are overwhelmingly popular. Yet we still have a huge challenge ahead of us, one that we cannot afford to fail. Those proclaiming a massive Tory majority as a foregone conclusion clearly haven’t been watching events very closely over the past two years. Donald Trump is the president of the United States, Britain voted to leave the EU, and Leicester City won the Premier League. Across the channel, Jean Luc Mélenchon, who heads a grassroots movement La France Insoumise or Untamed France, could be on the verge of making the second round in the French presidential election. A month ago he was polling at 10%. We live in an era that is defined by electoral upset and the inability of experts to predict events.

We should not underestimate the power of radical movements to beat the odds and break through from the outside – and Jeremy Corbyn’s Labour party is exactly that kind of movement. Nor should we underestimate the levels of anger at a system in which more than 16 million people have less than £100 in the bank, while the richest and multinational corporations are due to be given £70bn in tax breaks over the next few years.

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With a mass campaigning movement, Labour’s alternative can be communicated to voters in every part of the country, making this election the starkest choice an electorate has ever faced: do we want a Britain that works for the millions or the millionaires?

Momentum has designed some of the technologies that could help mobilise this campaign force. Our phone canvassing website allows activists to call our supporters from the comfort of their own homes to inform them about local campaigning sessions. Our Momentum carpool site enabled hundreds of activists to travel together to campaign in the recent byelections, helping Labour to knock on every single door in Stoke in one day.

As well as campaigning for Labour on the doorstep, Momentum activists have been organising more widely in their communities and providing solidarity with those facing the consequences of Tory vandalism. From supporting food banks, screening I, Daniel Blake on council estates, to helping to form credit unions and housing advice surgeries, Momentum activists have been filling the void created by Tory cuts and deepening Labour’s roots in communities across the country.

Before I started working for Momentum, I was a primary school teacher. I used to keep a supply of fruit and cereal bars in my stock room for all of the kids who came in hungry on a daily basis – an injustice that would be ended by Labour’s free school meals policy. That was in 2014, before a lot of the worst benefits cuts came through. In 2022, after another five years of Tory rule, and a Tory Brexit which threatens to further privatise our public services, deregulate our economy, and turn Britain into a tax haven for 1%, I can’t imagine what the state of Britain’s schools, and our society, will be.

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We all have a duty to ensure that this dystopia doesn’t become our reality. Momentum will be using innovative technologies and networks of hundreds of activists across the country to mobilise Labour’s mass membership, building campaigns from the ground-up, and reaching out to those who have long felt left behind by the political establishment.

We never said it would be easy, even if the dynamic energy and bottom-up approach of the Corbyn leadership campaigns felt exciting and transformative. We said it was necessary to change course from an approach that has seen support collapse for social democratic parties across the developed world.

Labour can win this, but we all have to join the fight. If progressives and Labour party members of all stripes come together to campaign for Labour we can elect the most progressive, transformative government in our country’s history.