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Does Twitter matter? The temptation is to say no. Its user base is small compared with Facebook—321 million monthly active users versus more than 2 billion—and a quick glance at the trending topics reveals its fractious, claustrophobic atmosphere. Yet as one dead fox proves, it does matter: On December 26, a single tweet by a British lawyer with 178,000 followers, announcing that he had killed a fox with a baseball bat, made the front pages of two major newspapers.

Yes, it was a quiet news day. But Twitter has become journalists’ easiest and most reliable source of cor-blimey (or OMG, to American readers) stories, because all of human life is there, and it’s searchable. It is also the world’s wire service: Just look at Donald Trump, who drops his unfiltered thoughts straight onto Twitter, confident that they will be picked up by journalists. For anyone interested in politics, it is the closest thing to a global community center, or a small-ads section—the virtual room where it happens.

All of this gives the social network—and its most active users—outsize power to shape the political conversation. Its influence can be seen in contests currently under way in the United States and Britain: the race to become the Democrats’ presidential nominee, and the struggle to succeed Jeremy Corbyn as leader of the Labour Party. Both risk being distorted by what we might call the “Twitter Primary.”

British tweeters skew left and toward remaining in the European Union, which reflects their demographic makeup. “On average social media users are younger and better educated than non-users,” wrote the researchers Jonathan Mellon and Christopher Prosser in 2017. Users were also more likely to live in cities, “particularly wealthier areas with younger populations.” This phenomenon has been more thoroughly studied in the U.S., where The New York Times has reported that “the views of Democrats on social media often bear little resemblance to those of the wider Democratic electorate.” Active political tweeters in America were whiter, more left wing, more likely to be college educated, and less likely to say that “political correctness was a problem” than primary voters as a whole. Given the faux-democratic promise of social media, it is ironic that it has created a new establishment with roughly the same tight demographic boundaries as the old one.

How does this new establishment use its power? In Britain, political tweeters assail BBC producers and reporters with charges of bias. They make accusations that politicians cannot ignore, hobbling candidates by promoting sticky controversies on subjects that are low priorities among mainstream voters. They have more of an effect on the left than the right because of Twitter’s demographics. (Members of right-wing parties tend to be older.)

Of course, it’s not unusual for candidates to tack toward the extremes in membership contests, believing they can move back to the center when facing a national election. But the demands of the Twitter Primary risk saddling politicians with fringe positions they will struggle to moderate later. The stridency of highly polarized voices online also has a chilling effect on less engaged and less confident tweeters. The echo chamber of social media reassures those extreme voices that they are in fact the mainstream, even convincing Labour activists that the party was not set for a wipeout in the general election—before it received its worst result in almost a century.

Here’s one example of the Twitter Primary in action. In December, the Labour politician Rebecca Long-Bailey wrote an article that was seen as her pitch to be the party’s next leader. It was published in The Guardian, a newspaper that backed Corbyn’s Labour, and Long-Bailey herself is the anointed successor of Corbyn’s right-hand man, John McDonnell. The piece was mostly bland, but one phrase stood out: “progressive patriotism.” The top Twitter results for that phrase show the tenor of responses from the left. “We're now an electorate that can only be bought with racism,” reads one tweet with 1,400 likes. “Or ‘progressive patriotism’, to give it its latest fancy name.” (In the piece that officially launched her campaign, Long-Bailey did not repeat the phrase.) Yet to read so directly across from “patriotism” to “racism” is a fringe position. Some 67 percent of Britons describe themselves as “very” or “slightly” patriotic.” Telling two-thirds of the country that they are secretly racist is a courageous electoral strategy.

And that is just the reaction to the presumptive heir to the Corbyn project. The Twitter Primary is harsher on candidates from other sections of the party. During the last leadership election, Corbyn was praised by the left for his principled opposition to the Iraq War more than a decade earlier. Jess Phillips, who is now among the candidates to succeed him, was so opposed to the conflict that she left the party. Nonetheless, because she has not supported Corbyn’s leadership since 2015, she is regularly described by self-identified left-wingers as a “Tory.”

The genuine fury from the left at people three inches closer to the political center reflects a turbocharged tribalism. Freud called this “the narcissism of small differences”; the legal scholar Cass Sunstein calls it “group polarization,” where “deliberation tends to move groups, and the individuals who compose them, toward a more extreme point.” In his 2019 book Conformity, Sunstein noted that “confident people are both more influential … and more prone to polarization.” One consequence of group polarization, he found, was that those who held a minority position, or had useful information that ran counter to the prevailing trend, stayed silent or were ignored. Their groups therefore made worse decisions.

The Twitter Primary drives its members to extremes, while chilling the speech of outsiders. An excess of certainty leads activists to bad decisions and misapprehensions. Spend enough time on Twitter and you could believe that Corbyn “won the argument” in December, despite losing the general election. The postmortem on Labour’s defeat risks being hampered by a pervasive sense on social media that the party didn’t really lose, not really: Well, everyone I know voted for Corbyn. Activists may intellectually concede the reality of the Conservatives’ 80-seat majority, but it doesn’t feel like the Tories won. And that means there is less reason for them to support a change in tactics.

The small-p politics of culture journalism is also affected by tweeters’ lack of awareness of being exceptions rather than representatives of mainstream opinion. The journalist Jesse Singal recently published a post arguing that “super-wokeness is mostly an elite phenomenon.” Singal noted that Dave Chappelle’s latest Netflix show was widely condemned in ways that suggested everyone was offended by it, although, as he wrote, “the best data we have suggest that the vast majority of Americans view political correctness as a problem … The opinions most commonly represented in mainstream progressive outlets are not held by the masses, including by the groups seemingly with the most at stake.” He’s right: Ultra-liberal attitudes to race and gender are indeed not held by the masses, including racial minorities. But, crucially, they are held by the peers of the journalists writing those pieces, with whom these journalists hang out on Twitter. Once again, the cloistered world of Twitter is creating a false sense of consensus.

There is, of course, nothing wrong with people having strong opinions on social media. (I may even have succumbed to this temptation myself on occasion.) But the distortions of the Twitter Primary reach far beyond the social network’s limited audience—into all the organizations that allow Twitter to guide their journalism. Such outlets, in these tough economic times for media, are almost everywhere. After all, the proverbial water cooler is right there in reporters’ fifth browser tab.

What’s the answer? First, activists on Twitter should understand that their opinions, though valid, are not as widely shared as they may believe, even among their own political allies. They should resist the urge to assume that they are representative of mainstream opinion, that they “own” left and liberal parties, or that they have the sole right to rule on what is offensive. Using Twitter makes you exceptional. Being highly politically engaged makes you exceptional. That can be a neutral fact—as long as it is recognized.

Second, there is no point in demanding that journalists get out of the “Westminster bubble” or the “East Coast bubble” if they’re still stuck in the Twitter bubble. It is a place where a fox murder is the biggest news of the day, patriotism is racism, and Jess Phillips is a Tory. In other words, it’s nowhere close to reality.

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