Jonah Peretti, the C.E.O. of BuzzFeed, has announced that the Web site won’t run ads for the presumptive Republican Presidential nominee, Donald Trump. Will other companies follow suit? Photograph by Bodo Marks / picture-alliance / dpa / AP

On Monday morning, employees of BuzzFeed received an e-mail from the company’s C.E.O., Jonah Peretti, informing them of an unusual business decision: BuzzFeed had told the Republican National Committee that it would not accept ads for the presumptive Republican Presidential nominee, Donald Trump. This wasn’t a meaningless stunt. In April, the Committee had signed a deal to run Republican political ads on BuzzFeed prior to the general election—an agreement worth more than a million dollars, a source told Politico. “We certainly don’t like to turn away revenue that funds all the important work we do across the company,” Peretti wrote in his e-mail, which BuzzFeed later published. “However, in some cases we must make business exceptions: we don’t run cigarette ads because they are hazardous to our health, and we won’t accept Trump ads for the exact same reason.”

Peretti isn’t the first high-profile executive to speak out against Trump. Meg Whitman, the C.E.O. of Hewlett Packard Enterprise and a prominent Republican, has been particularly outspoken, calling the candidate a “dishonest demagogue” whose proposed policies could drive the United States into a recession. But executives have, by and large, avoided explicitly criticizing Trump. Facebook’s C.E.O., Mark Zuckerberg, and Tim Cook, the C.E.O. of Apple, have made comments that seemed to take aim at Trump’s proposal to bar Muslims from the country, but they didn’t name the candidate. Even Salesforce.com’s C.E.O., Marc Benioff, a Hillary Clinton supporter and an outspoken critic of recent laws that have restricted the rights of L.G.B.T. people, has been circumspect. Asked about Trump on CNN, he said only that Whitman’s assessment is “probably true” before changing the subject. Peretti’s suggestion that Trump can literally make us sick goes much further.

More notable still is the directness with which Peretti tied BuzzFeed’s business decision to Trump himself. In the past several weeks, Microsoft, Coca-Cola, and HP, previous funders of the Republican National Convention, have acknowledged that, after being lobbied by activists, they’re either not supporting this year’s Convention or have significantly cut their funding compared with 2012. But those companies, when they’ve addressed the rationale for their decisions at all, have framed them in the most neutral of terms; none have named Trump. A blog post from Fred Humphries, a vice-president for government affairs for Microsoft, explains, “Based on our conversations with the Republican National Convention’s host committee and committee on arrangements, we decided last fall to provide a variety of Microsoft technology products and services instead of making a cash donation.” (Fair enough, though the post acknowledges that Microsoft is giving cash support to the Democratic National Convention.)

Rashad Robinson, a spokesman for the Color of Change PAC, one of the groups that has been pushing companies not to sponsor the Republican Convention, told me that even in his private phone conversations with company representatives, “They’ll talk about who they are as a company and the rhetoric that they don’t value, but they don’t mention Trump.” The Color of Change PAC had nothing to do with BuzzFeed’s decision to take an explicit stance on Trump, but Robinson called it “different” and “powerful.”

Peretti’s specific argument, in his letter, was that Trump’s policies would be bad for his employees and, in turn, his company. “The Trump campaign is directly opposed to the freedoms of our employees in the United States and around the world and in some cases, such as his proposed ban on international travel for Muslims, would make it impossible for our employees to do their jobs,” he wrote. The explanation echoed a similar point made by other executives, earlier this year, after North Carolina and other states passed laws seen as harmful to L.G.B.T. rights. In an open letter urging the governor of North Carolina to change his mind about a law that would prevent transgender people from using the bathroom of their choice, more than eighty executives, from Apple, Pfizer, and other companies, wrote, “The business community, by and large, has consistently communicated to lawmakers at every level that such laws are bad for our employees and bad for business. This is not a direction in which states move when they are seeking to provide successful, thriving hubs for business and economic development.” The North Carolina letter and other similar protests prompted James Surowiecki to write that the companies were “pushing a progressive agenda in the conservative heartland.” Several companies even stopped doing business in states that passed discriminatory laws.

Thus far, businesses haven’t broadly opposed Trump, despite his calls to keep Muslims out of the U.S., his disparagement of immigrants from Mexico and other Latin-American countries, and now his attacks on Gonzalo Curiel, the federal judge who is presiding over a lawsuit against Trump University. One explanation is that this is because Trump’s proposals are, at this point, only proposals; in order to write them into law—and so directly affect the way companies operate—he would need the support of Congress, so a strong corporate response at this time would be premature. But there could be other reasons. For one thing, the governor of North Carolina is far less influential than a man in the running to be the head of state of the most powerful country in the world: “These corporations, while they’re not going to tell this to us, are afraid to piss Donald Trump off if he might be the next President,” Robinson said. There are also far, far more supporters of Trump than there are residents of, say, North Carolina—and voters are also potential customers. Zuckerberg has noted in the past that Trump has more Facebook followers than any other Presidential candidate.

A day after BuzzFeed announced its stance, no other similarly high-profile companies have followed suit. Nor have any previous sponsors of the Republican Convention said that they are pulling back this year specifically because of Trump. But Robinson is hopeful that internal pressures, especially in Silicon Valley, which has a relatively progressive workforce, could prompt action down the road. “We know from our campaign that many companies in Silicon Valley are having to deal with their employees, who are not happy, and a lot of our advocacy has been directed at employees, meaning, running Google ads targeted at Google employees and Facebook employees,” he said. It was less clear how much his message was resonating outside of places like Silicon Valley and the East Coast. For a serious anti-Trump movement to develop among businesspeople, Trump’s chances of winning the election will probably have to diminish significantly, thus lowering the risk of repercussions. If that were to happen, businesses would be following public sentiment rather than helping to shape it—a less risky proposition, but also a less significant one.

So while Peretti’s action and the campaign directed at the Convention are making headlines, it’s not clear how much of an impact they’ll have in the end. A spokesman for the Republican National Committee told CNN that it “never intended to use” the space reserved on BuzzFeed for ads. And, certainly, plenty of other outlets are happy to take the committee’s money. Meanwhile, Emily Lauer, a spokeswoman for the host committee of the G.O.P. Convention, told me that fund-raising efforts are going well: fifty-seven million dollars have already been committed, out of a needed sixty-four million dollars. “Overall, the effect of Mr. Trump becoming the presumptive nominee has been minimal,” Lauer wrote in an e-mail. “A handful of companies have slowed their decision making process and have told us they are waiting a bit longer to see how things play out. And only one company has backed away from their committed sponsorship to the Cleveland Host Committee as a result of Mr. Trump becoming the presumptive nominee.” (She declined to name the company.)

Those who are eager to see businesses take a stand against Trump can perhaps take heart from a couple of recent Trump-trolling advertisements by companies that see obvious benefit in opposing him. A spot by the Mexican airline AeroMexico, for example, evokes Trump’s rhetoric about immigration and walls before making the (dubious, yes) case that air travel defies borders. And an ad by an Argentinian TV channel for its broadcast of this year’s Copa America soccer tournament, which is being held in the U.S., combines images of Argentinian soccer stars with Trump’s disparaging comments about Latin Americans. “We have no protection,” Trump says, over footage of Lionel Messi dribbling past his opponents. “The best they can do,” the commercial concludes, “is not let us in.”