The victory of Joe Biden in the US presidential election and Keir Starmer’s decision to suspend Jeremy Corbyn from the Labour Party represented the end point of the Sanders and Corbyn ‘moments’ respectively. In the US, the Left is fighting against corporate Democrats who are seeking to blame them for Joe Biden’s down-ballot failures. In the UK, socialists are fighting for the right to simply exist within the Labour Party.

The movements that emerged over the course of these moments, however, live on. The challenge socialists on both sides of the Atlantic face today is how to build movement power into something more long-lasting – to develop an institutional base for socialism in their respective national contexts. Socialists must be under no illusions that liberal sections of these centre-left political parties would like to destroy them. On a post-election conference call in the US, former CIA agent and current Congresswoman Abigail Spanberger even demanded that the Democrats never say the word ‘socialism’ ever again.

This is a blatant attempt to rewrite history. As Alexandria Ocasio-Cortez pointed out recently in a scathing interview, progressives were central to Biden’s victory. Their grassroots organising efforts helped to produce record turnouts across the country. This was particularly the case in swing states like Minnesota – where The Washington Post covered Rep. Ilhan Omar’s efforts in the weeks leading up to election day. According to Ken Martin, the chairman of Minnesota’s Democratic Farmer-Labor Party,

She doesn’t need to increase turnout here to win her race. She could take a vacation and she’d get reelected, easy. But she recognises that she has a responsibility to drive up turnout; it’s really important for all of our statewide races, especially the presidential race. She does really intensive, face-to-face contacts, with a lot of personal relationship-building, and building long-term power with communities of colour. And, look, a lot of politicians don’t do that.

There is also a direct line between the enormous Black Lives Matter protests earlier this year and increased turnout from African-American communities, particularly in larger urban areas such as Detroit and Philadelphia which were crucial to Biden’s success. And across the board, left-wingers were an important part of the Democratic coalition: candidates who backed Medicare for All – even in areas that leaned Republican – won re-election in every instance. Fox News even released an exit poll on election night showing that more than 70% of voters favoured some form of government-run healthcare plan, and the same number favoured public investment in decarbonisation.

But facts don’t matter to the anti-socialists, who are rightly concerned that the Left came far too close to power in recent years. They know that their meek brand of corporate centrism – as well as Trump and Johnson’s reactionary brands of corporate nationalism – would be rendered irrelevant if voters were ever offered a real choice between social-democratic reform and the status quo.

The Corbyn and Sanders movements came close to making the right-wing of the Labour and Democratic Parties lose power for a generation – and now the anti-socialists within these parties are going to do everything in their power to prevent this happening again. Corporate Democrats and Labour right-wingers will declare all-out-war on the progressive wings of their parties in the coming months and years. It is more important than ever for the Left to prepare for this fight by building institutional power.

Socialists too often approach the battles waged by the Right with naivety. Most grassroots activists – entirely reasonably – wonder how anyone could be so fervently opposed to socialised healthcare and preventing climate breakdown. Surely, they think, if we make our arguments well enough, we’ll win them over to our way of thinking.

But this misunderstands the role of right-wing politicians within centre-left political parties. As has been made abundantly obvious from the fates of the Labour MPs who split from the party at the last election, these people exist to serve corporate interests – Chris Leslie has joined the industry body representing debt collectors, Chuka Umunna has joined a lobbying firm, and Angela Smith has joined a private water company after decrying Labour’s proposals to nationalise the sector.

As individuals, they – and their peers who remain in the Labour and Democratic Parties – are largely useless. They’re incapable of making coherent arguments, they generally lack charisma and they’re far too focused on their personal career success to act as compelling leaders. But they’re extremely important to ensuring that the injustices of capitalism are perpetuated.

Without the right of the Labour and Democratic Parties, who would protect the interests of the enlightened elite from the fury of working people? When these people decry ‘populism’, this is what they mean. They see their roles as defending the status quo against popular pressure and marginalising the Left at all costs. They are usually well remunerated for doing so.

Arguing with the political centre will never be enough – and as long as the role of socialists in British and American politics is limited to fighting with centrist blue-ticks on Twitter, we’ll be consigned to permanent irrelevance. They don’t care about facts, they don’t care about accountability, and they don’t care about democracy. They only care about one thing: beating the Left into oblivion.

Socialists could learn a thing or two from this attitude. We need to build real institutional power if we’re going to withstand the onslaught of the coming years and reverse it in the years after that. Healthy reflection on the Left’s recent focus on electoralism is one thing, but leaving the battlefield of party politics altogether is quite another. We need to be in the game, if only to ensure that anti-socialists on both sides of the Atlantic don’t succeed in permanently destroying those fighting against austerity, corporate power and racism.

Trade unions, combined with the Democratic Socialists of America in the US and Momentum in the UK, provide a base for socialists in both countries. But much of the time the leaders of left-wing movements seem more focused on fighting each other than they do with building left power. At least in the US, the leading lights of Congressional Left provides somewhat more hope than the Parliamentary Left in the UK, which has meekly consented to its own marginalisation.

On the ground, it is critical that activists continue to build power on the streets, in their communities and in their local parties. The Corbyn and Sanders moments may be over, but the socialist movement remains strong; too strong for the liking of the anti-socialists in the Labour and Democratic Parties. The fact that they remain intent on destroying us is an indication of our potential. But it should also remind us that now is the time to organise.