The emboldening of far-right groups in Britain ranks among the most insidious byproducts of the 2016 Brexit referendum. Commentaries tend to focus on networking efforts and fundraising. Yet few have examined how the language being used around Brexit, not only on the streets but also in Parliament and the media, has helped the far right to mobilize followers and increase the potential for violence.

In early April, former Conservative member of Parliament Sarah Wollaston revealed that she had been targeted with death threats after campaigning for a second referendum. She wasn’t the first. Anna Soubry, another former Tory MP whose pro-European Union stance led to her being heckled outside Parliament with shouts of “Nazi” and “traitor,” warned that frequent threats had prevented her from returning home. More MPs have since said they are receiving death threats on a daily basis.

Right-wing rhetoric tends to draw much of its energy from the device of “us vs. them,” often framing politicians as working in the service of foreign powers against their own people. A report in February by the civic group Hope Not Hate warned of a stark shift in far-right rhetoric toward a narrative of “betrayal,” one that has targeted female politicians in particular. It is clear that even in Britain, despite its centuries-long experience with open democratic politics, such narratives can be deadly. To look at the conversation around Brexit since the murder of parliamentarian Jo Cox in 2016 is to understand not only that nothing was learned from the events that led up to her killing, but also that political leaders who understood the strategic value of anger were willing to use the same kind of incendiary rhetoric that presaged her death to mobilize people behind their agenda.

In the wake of Cox’s death, the likes of former foreign minister Boris Johnson and UK Independence Party founder Nigel Farage, who baited Leave voters with fears of besiegement by immigrants, offered no recognition of the hostile, even lethal, climate created by their words. Rather, the specter of “traitors” haunting Parliament intensified. Late last year, Farage described the United Kingdom’s Brexit negotiation team as “the enemy within.” A Tory backbencher said of Theresa May in the Sunday Times last October: “The moment is coming when the knife gets heated, stuck in her front and twisted. She’ll be dead soon.”

Threats against politicians coincide with a widening space in post-referendum Britain for racist or other forms of exclusionary language. A Conservative Party panel last year used a free-speech defense to clear Johnson of any wrongdoing after his comments in the Daily Telegraph that women wearing burqas might resemble “bank robbers.” Spectator columnist Rod Liddle then opined that “there is not nearly enough Islamophobia in the Tory party.” In the Times, Melanie Phillips wrote that Islamophobia “is a fiction to shut down debate.”

Through their writing, whether in language direct or implied, these figures have provided the raw material that helps to shape and sanction the kind of exclusionary ideologies used by those who aim for conflict. Labour councilors and members who indulge in anti-Semitism have contributed, too. Their rhetoric excites fears in people already inclined to see particular communities as threatening, and the imagery they evoke draws an immediate and emotive link between particular identities and the threat they pose. Actual calls for violence aren’t always necessary — one can set the tone without giving orders.

The language used by figures in Parliament and the media has helped to set up pro-E.U. politicians as willing abettors of societal breakdown, as happened with Cox before her murder. Far-right groups who feed off the deepening fissures around Brexit have been empowered by a changing sense of what is acceptable language in British public life. Britain’s counter-terrorism chief, Neil Basu, has cautioned that far-right politicking is generating a “permissive atmosphere” in Britain in which the potential for violent behavior builds.

The emboldening of fringe movements is the predictable outcome of a critical loss of confidence in government. With the political center in Britain weakening, the magnet that had drawn forces toward the middle ground is losing its pull. Far-right groups are proving that, away from Westminster, language plays a vital role in elevating the visibility and status of those who lack genuine electoral power, and who can manipulate the divisions exposed by the referendum to maneuver themselves into more central positions.

Hope Not Hate quotes author and politician Vernon Bartlett, who, writing as World War II loomed, said of fascism: “[It] starts by being an emotion; it only develops a plan and a philosophy after the emotional crisis has reached its height.” Particular words and images, even if used casually, can have profound consequences. Made at moments of high public anxiety, references to politicians as traitorous Nazis tap into emotions that are powerful enough to trigger actions beyond those contemplated in their words.

Some within the political leadership in Britain appear ignorant of the fact that the turn to violence often begins with a shift in the language. Others know it only too well. Britain has already witnessed an assassination designed to silence one such “traitor.” Three years after Cox’s murder, those narratives are growing louder. We should not be confident that it won’t happen again.