In what’s been deemed the “most expensive divorce in history,” British voters made the historic decision in June to leave the European Union. And like most political campaigns these days, it wouldn’t have been complete without the two sides duking it out on social media. Even the decision’s nickname, largely dubbed “Brexit” by the media, was a pithy neologism perfectly suited to social media.

Given the importance of social media in any political campaign today, it’s no surprise that both the Remain and the Leave camps leveraged social media to win hearts and minds. Younger voters, typically more active on social media, tended to vote Remain by significant margins. According to British Pollster YouGov, 75 percent of voters between ages 18 and 24 voted Remain. Yet despite younger voters’ overwhelming tendency to vote Remain, the Leave campaign was – ironically – far more successful at harnessing social media to galvanize its supporters.

On Instagram, Brexit Dominated

According to an analysis of the Brexit debate on Instagram, E.U. sceptics and Leave supporters dominated the discussion. Across the most popular hashtags, 32 percent of users shared clear anti-E.U. views, compared to just 12 percent sharing pro-E.U. or Remain sentiments. Moreover, Leave supporters tended to be “more passionate, active and outspoken” in their behavior, generating almost five times as many posts as the Remain voters. Interestingly, Leave sympathizers were far more active on Instagram, despite generally being older and seemingly less social media savvy than the Remain camp.

Though political and corporate campaigns often rely on user-generated content on Instagram to spread awareness, the Brexit vote offers a cautionary tale. Even though young people tend to side with more progressive values, politicians and companies can no longer assume this demographic will passionately share their views on Instagram, one of the most popular social media tools among younger demographics. Corporate and political campaigns still need to court younger supporters through hashtag campaigns and compelling visual content to drum up support and drive awareness.

Slick Videos Missed the Mark

Neither campaign left messaging up to chance, turning to activists and some of Britain’s best-known advertising agencies to produce videos for social media. The Leave campaign successfully leveraged videos from grassroots operatives, including a 70-minute documentary about the E.U.’s flaws by Martin Durkin, an anti-E.U. filmmaker. The video was viewed 1.2 million times on YouTube and according to The Financial Times, “sliced into bite-sized clips by activists and distributed via Twitter and Facebook.”

The Remain campaign, by contrast, relied more heavily on agency-produced videos featuring celebrities. In a heavily panned ad attempting to mimic how young people speak, the “g” was dropped at the end of words (“workin’,” “earnin’,” “makin’,” “votin’”). This led to a meme featuring young people with the headline “We love to be patronised” spreading across social media. Adam & Eve DDB, one of Britain’s most well-known communication and branding agencies, produced a pro-Remain ad starring Keira Knightly, Big Narstie and Lily Cole with the line “It takes five seconds to mark an X in a ballot box. It takes five seconds to stop others f****** with your future.” The use of “f******” was clearly intended to appeal to younger voters, but it reeks of pandering when the source is a political campaign.

The Remain campaign, unfortunately, missed the mark yet again with its video strategy. While the celebrity-filled videos were slick and shareable, they lacked the authenticity of voter-generated content. Millennials are inherently cynical of ads they perceive as condescending or pandering to them. By relying more heavily on grassroots operatives than polished agency-produced videos, the Leave campaign more effectively galvanized its base.

Brexit – A Cautionary Tale for Presidential Candidates

As America’s presidential election is in full swing, both sides should pay heed to the pitfalls and successes of the Brexit social media wars. The takeaway for political and corporate campaigns moving forward? Don’t pander to young people. Encourage them to create their own shareable content, and don’t assume that young progressives will actively support your campaign on social media. Millennials need to be courted with authentic content, arguably more so than any other demographic.