We’re always hearing about “firestorms of protest,” but they seldom involve actual fire. In November, though, people who owned New Balance sneakers began setting them alight, posting videos of flaming footware to social media, and calling for a boycott of the company. Like so much else these days, it’s because of Trump. The night that he was elected, a New Balance spokesman told the Wall Street Journal, “With President-elect Trump, we feel things are going to move in the right direction.” The spokesman was actually making a fairly limited point about trade policy. Trump has promised to scrap the Trans-Pacific Partnership, a deal secured by President Obama that would reduce trade barriers between many Pacific Rim countries. That suits New Balance, which still manufactures some of its shoes in the U.S., but good luck trying to communicate such subtleties in the current climate. New Balance suddenly found that its support for American workers-P.R. gold, you would have thought-had led it into contentious territory. New Balance hasn’t been the only corporate victim of a hyperpolarizing election season. After Pepsi’s C.E.O., Indra Nooyi, said that company employees were “crying” after Trump’s victory, conservatives called for a boycott. (The cause was aided by a viral fake-news story claiming that Nooyi had told Trump supporters to “take their business elsewhere.”) A couple of weeks later, Kellogg’s became the target of a conservative boycott, for yanking its advertising from Breitbart News. There’s a long history of corporate boycotts: the labor movement used them during strikes at the turn of the twentieth century, and they’ve been common since the nineteen-sixties. But, until now, boycotts have usually been staged in response to specific corporate practices. The United Farm Workers, in the mid-sixties, organized the famous grape boycott in order to get farmers to stop relying on underpaid, non-union workers. Greenpeace organized a boycott of Shell, in 1995, to stop the company from dumping an old oil platform at sea. And, in the nineties, Nike faced a boycott over its reliance on sweatshop labor. By contrast, the Trump boycotts, from both the left and the right, have been driven by issues extraneous to the targets’ core business practices. There are antecedents: a few years ago, L.G.B.T. activists went after Chick-fil-A after its president voiced his opposition to gay marriage. But there’s something new about the speed and ferocity with which people now respond to corporate statements or signals. You can see it as the next logical step in the evolution of what’s sometimes called political consumerism. In the past few decades, we’ve grown accustomed to holding corporations responsible for their labor practices and environmental records. So it’s not surprising that they are being called to account for their real or imagined political messages. If we are indeed entering a Trump-fuelled era of consumer activism, it’s bad news for companies. Boycotts are not just futile griping; they often work. The U.F.W., Greenpeace, and anti-Nike boycotts were all successful. A study by Brayden King, a professor at (aptly) the Kellogg School of Management, found that, during high-profile boycotts between 1990 and 2005, a company’s stock price fell, on average, every day that the boycott was in the news. King also found that more than a third of the boycotted companies ended up changing their behavior in response to the protest. Perhaps his most striking finding was that boycotts usually had only a small impact on sales. Bad publicity and worried stockholders were enough to bring a company to heel. Thanks to social media, boycotts are easier to organize than ever. They used to face a classic collective-action problem: taking part makes sense only if everyone else is. Unlike a street protest, a boycott isn’t inherently visible: you can’t really watch someone not buying Frosted Flakes. Now you can see how many people have signed online pledges, and view videos of burning sneakers. All this helps project a feeling of momentum and critical mass, which in turn attracts more participants. The obvious solution for corporations is to say nothing controversial. But in the Trump era a truly neutral position is hard to find. Pepsi’s Nooyi has agreed to join Trump’s so-called Strategic and Policy Forum, a group of C.E.O.s who will meet with him periodically. Does that mean Pepsi will go from being the target of conservative attacks to being the drink of choice for the alt-right? Kellogg’s stopped advertising on Breitbart after being spotlighted by Sleeping Giants, a social-media campaign that is pushing brands to cut their ties to the site. But, in trying to avoid one consumer backlash, Kellogg’s walked straight into another. Companies are used to facing pressure over where they advertise. But now they have to worry about where they don’t advertise, too. Trump’s victory has created a political realm in which tens of millions of people feel that if you’re not with them you’re against them. That’s a curse for companies that aim at a mass market, America’s traditional strength. It’s hard to be all things to all people in an us-versus-them world.