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Emily Parker is the author of “Now I Know Who My Comrades Are,” a narrative account of social media activism in China, Cuba and Russia.

Not so long ago, many of us were celebrating social media’s power to topple oppressive leaders. Those days are over. Today it’s far more common to read about how social media echo chambers are destroying democracy. Barack Obama highlighted the dangers of filter bubbles in his farewell speech. Harvard Law Professor Cass Sunstein has written a whole book on the topic. It opens with the line: “In a well-functioning democracy, people do not live in echo chambers or information cocoons.”

The argument against echo chambers is clear. A combination of algorithms and personal choices allow us to focus on content that confirms our beliefs. On social media we huddle with those most like us, using our Twitter and Facebook feeds to preach to the converted.

It’s true that echo chambers can obstruct the flow of information, and that’s a problem. But those echo chambers can also be a formidable tool for political resistance. Where else do you have such immediate access to hundreds, thousands or even millions of people that agree with you? The key is to use social media for mobilization, not persuasion.

Internet dissidents in authoritarian countries have long understood this. In countries that restrict freedom of assembly, dissidents find each other on the Internet. In China and Russia, the opposition uses social media to organize among themselves, not to convince the other side. “I don’t waste my time arguing with leftists on the Internet,” a Chinese activist once told me — and you can hear similar sentiments in the United States. A Black Lives Matter activist told me that social media was for fostering black solidarity, not for changing white people’s minds.

Solidarity is essential for political action. You probably won’t attend a protest, for example, if nobody else is going to be there. In your echo chamber, at least, you know you are not alone. That knowledge is not enough for real political change, but it’s a start. After the presidential election, large groups of people clustered on the Internet, looking for somewhere to direct their energy. Social media can point those people toward a specific set of actions.

President Trump has skillfully used social media to galvanize his supporters, but the resistance is using the same tool to fight back. Social media helped drive people to the Women’s March over inauguration weekend, and it also directed Americans to airports across the country to protest Trump’s executive order on immigration and refugees. A #DeleteUber campaign, which protested the company’s lack of solidarity with airport protesters, spurred more than 200,000 people to delete their accounts. Uber Chief Executive Travis Kalanick subsequently quit Trump’s economic advisory council. A “Grab Your Wallet” campaign urged people to boycott products with ties to the Trump family, and it may have contributed to Nordstrom’s decision to drop the Ivanka Trump clothing line.

Democrats have also been using social media to influence Congress. Twenty-first-century technology is surprisingly effective for getting people to pick up a telephone and flood congressional offices with calls. Social media campaigns are also useful for ginning up donations, helping to raise serious money for the American Civil Liberties Union and other organizations.

Fine, some will argue, but so what? We already know that social media is good for low-cost, short-term actions. But today’s echo chambers can fan the kind of energy needed to achieve broader strategic goals. Owen Ellickson, a comedy writer whose Twitter following soared after he began parodying Trump, turned his feed into a kind of progressive hub. “If you can use social media to psych up your team, that can have big real-world consequences,” he said.

An organization called Swing Left intends to prove that point. Swing Left’s goal is to help Democrats win back the House in 2018. You type in your zip code on their website to find the swing district closest to you, and then you can sign up to learn how to help. Social media helped Swing Left quickly build a base. By Jan. 22, the New Yorker reported, 100,000 people had signed up for Swing Left updates, a number that has surged since. Immediately after the House vote on a bill to replace Obamacare, tens of thousands of grass-roots donors contributed more than $2 million to support the Democrats running against the Republicans who supported the repeal.

David Klatt, social media director for Swing Left, told me that the organization doesn’t use its Twitter feed to try to win over Republicans. The first step is “mobilizing people who want to see Democrats elected in swing districts.” As he puts it, “Left is in the name.”

Nobody likes the idea of echo chambers. They amplify fake news. They serve as breeding grounds for terrorists and white supremacists. They also widen the political divide, which can have serious electoral consequences. Make no mistake: If you want to win an election, you have to communicate with people on the other side. But maybe social media isn’t the best place to do that.

Twitter, with its flame wars and character limits, is just not an optimal tool for persuasion. How often do you see liberals on Twitter getting Trump supporters to change their views, or the other way around? What social media can do is urge people to shut their laptops and go knock on doors to talk to voters, for example. “One of our social media goals is to empower our volunteers to show up and do the hard work that is required to flip a House seat blue in a swing district,” Klatt said. Social media communicates goals and calls to action, but “the real effective organizing happens on the ground.”

In other words, don’t spend all your time arguing with people on the Internet. If social media won’t bridge the political divide, use it to close ranks.