With gruesome images of Israel’s lethal crackdown on Gaza spread across the world, Palestinian activists are calling for a renewed push around a hard-hitting pressure tactic against Israel: Boycott, Divestment, and Sanctions (BDS). European and Arab leaders are harshly criticizing Israel for killing dozens of Palestinian protesters in Gaza. Now Palestinians and their supporters are hoping the outcry will lead to more support for their campaign to boycott Israel and turn the country into an international pariah.

At issue is the pro-Palestinian BDS movement. Its supporters, who take inspiration from the campaign that international activists used to pressure South Africa to end apartheid, work to punish Israel economically and isolate it politically because of its continued occupation of the West Bank, de facto control of Gaza, and mistreatment of Palestinian citizens of Israel.

BDS has had some high-profile successes in recent months, such as when the pop star Lorde canceled a concert in Tel Aviv in December in response to pressure from BDS activists.

Now pro-Palestinian activists online are calling for an escalation in international BDS campaigns in response to the killings in Gaza. Mustafa Barghouti, a member of the central council of the Palestinian Liberation Organization, told BBC’s Newshour on Monday that BDS and popular nonviolent resistance are “the best two instruments to force Israel to change its policies.”

BDS is highly controversial in Israel and the American Jewish community. Some of its critics describe it as anti-Semitic, arguing that it unfairly singles out Israel for human rights violations when other countries have worse records, or that it’s a crude tool that can alienate people sympathetic to its cause. Its defenders argue that since BDS arose in response to Israel’s treatment of Palestinians, its focus on Israel is logical, and that its criticism is rooted in the country’s violations of international law, not Israel’s character itself. The movement officially condemns all forms of bigotry, including anti-Semitism.

Experts have estimated that BDS could lop anywhere from $15 billion to $47 billion off the Israeli economy over the next decade. That financial toll could grow if the Gaza killings lead to a spike in support for BDS efforts globally.

“Every time Israel blatantly violates Palestinian rights, there is another BDS victory,” Noura Erakat, a Palestinian-American legal scholar of human rights at George Mason University, told me.

BDS is a sprawling movement that covers a lot

The BDS movement says its goal is to push the Israeli government to meet three main demands. In its own words, these are:

1. Ending its occupation and colonization of all Arab lands and dismantling the Wall. International law recognizes the West Bank, including East Jerusalem, Gaza and the Syrian Golan Heights as occupied by Israel. 2. Granting Arab-Palestinian citizens of Israel their right to full equality 3. Respecting, protecting and promoting the rights of Palestinian refugees to return to their homes and properties as stipulated in UN resolution 194

BDS has been around for more than a decade, and it enjoys high levels of support among Palestinians, in part because it seems to have better prospects of effecting change than the divided and anemic Palestinian political leadership. But it’s really in the past few years that it’s begun to gain international prominence, evolving from a fringe movement to one that worried Israeli and Jewish leaders are condemning more and more strongly.

“Those who wear the BDS label should be treated exactly as we treat any anti-Semite or bigot. They should be exposed and condemned. The boycotters should be boycotted,” Israeli Prime Minister Benjamin Netanyahu said in a speech to the American Israel Public Affairs Committee (AIPAC) in 2014.

The BDS movement has some wins on the world stage, including the European Union’s creation of guidelines that require goods exported from Israeli settlements in occupied Palestinian territories to be labeled as such (as opposed to simply being labeled as from Israel), a policy that’s expected to hurt Israeli exports. Norway’s $810 billion Government Pension Fund Global, the world’s largest sovereign wealth fund, blacklisted two Israeli companies over their involvement in settlement building in East Jerusalem.

The movement’s impact in the US has been more mixed. The United Methodist Church’s $20 billion pension board, the biggest pension fund asset manager in the US, blacklisted the five largest Israeli banks.

The student councils of most of the University of California campuses have voted for divestment from companies making money from the settlements, as have student organizations at New York University, George Washington University, and Barnard College. The National Women’s Studies Association and other academic groups in the US have voted to boycott Israeli universities. In 2013, legendary physicist Stephen Hawking refused to attend a conference in Israel in solidarity with BDS.

In the aftermath of the Gaza violence, the White House didn’t echo its European allies in condemning Israel or calling for an international probe; it instead put all the blame on the Palestinians.

BDS is targeting companies where it hurts

There are signs that BDS can do more damage to companies by harming their reputations than by getting large numbers of people to boycott their products.

Take the Israeli company SodaStream, which manufactures a kitchen appliance for carbonating water at home. BDS supporters targeted it for operating a factory in the West Bank, and the company ultimately shut down down the facility in 2015. Its CEO, Daniel Birnbaum, said the move was a financial decision that wasn’t tied to the BDS campaign, which he said had only a “marginal” effect on its business.

But according to testimony Birnbaum submitted to Congress, the BDS movement hit the company squarely in the pocketbook. “There is absolutely no doubt that our reputation as individuals and as a company was compromised because of our association with the lies and allegations directed at us from the BDS,” Birnbaum said.

SodaStream’s experience gets to the heart of the matter here. While BDS’s actual financial impact on foreign and Israeli businesses in Israel so far is extremely small, its campaigns can deal a significant blow to a brand’s reputation over time. And that’s enough to change the behavior of institutions that want to maximize their bottom line.

So while BDS campaigns aren’t yet close to capable of bringing Israeli businesses to their knees, in the aggregate, they could easily become a substantial factor in the calculations that investors worldwide make about Israel’s business climate.

Many Jews see BDS as anti-Semitic

Steven M. Cohen, a research professor at Hebrew Union College Jewish Institute of Religion, told me that to the average Jew, BDS is threatening because it comes across as “anti-Israel.”

Although BDS has a formal mission statement, in reality, it serves as a banner for a number of groups and individuals with a wide variety of views and motives. And the movement has attracted members who push for goals that go further than getting Israel to comply with international law.

As Vox’s Zack Beauchamp has written, “While the movement takes no official position on how to end the Israel-Palestine conflict, one of its co-founders, Omar Barghouti, has called for unifying them into a single state, which would mean dissolving Israel as a Jewish state.”

That’s fed concerns among some Israeli observers that the thrust of BDS is ultimately at odds with a two-state solution. “Chief spokespeople for the state of Israel argue that the Palestinians and their supporters are not looking for freedom and to live peaceably within Israel, but that they’re trying to take over all of Israel or wipe out the Jewish state,” Cohen says.

BDS advocates argue that the movement doesn’t stand by any specific political future, and instead focuses on compliance with international law.

Many supporters of Israel have also been dismayed by the BDS movement’s successes in, for instance, getting Lorde to cancel her planned concert in Tel Aviv amid public pressure from BDS activists and fans.

“I’ve received an overwhelming number of messages and letters and have had a lot of discussions with people holding many views, and I think the right decision at this time is to cancel the show,” Lorde said in a statement. “I’m not too proud to admit I didn’t make the right call on this one. I’m truly sorry to reverse my commitment to come play for you.”

After she pulled out of the concert, a prominent American rabbi, Shmuley Boteach, ran a full-page ad in the Washington Post calling her a “bigot,” while a group of more than 100 musicians, actors, and directors signed a public letter supporting her.

Israel’s recent victory in the Eurovision Song Contest — its first since 1998 — caused dismay among BDS advocates, some of whom basically hoped that Israel would be barred from participating.

The fact that Israel, as the defending champion, will host next year’s competition is angering them further.

“Israel will use next year’s Eurovision to try to legitimize its occupation, ethnic cleansing and illegal annexation,” Ali Abunimah, founder of the website Electronic Intifada, tweeted on Sunday. Europe, he writes, is “giving this propaganda its full Trump-like support.”

Sometimes specific one-off boycotts by artists have been confused with support for BDS, — like when Israeli-American actress Natalie Portman canceled her visit to Israel to receive the Genesis Prize, a prestigious award sometimes referred to as the “Jewish Nobel,” in April.

The Genesis Prize, in a statement, said that “recent events in Israel have been extremely distressing to her,” adding that “she does not feel comfortable participating in any public events in Israel.” This was widely interpreted as a reference to the crisis on the boundary between Israel and the Palestinian-populated Gaza Strip, in which Israeli troops have shot a number of Palestinians during occasionally violent demonstrations near a border fence.

Israeli Culture Minister Miri Regev blasted the decision, saying Portman had “fallen into the hands” of the BDS movement; Oren Hazan, a member of Israel’s parliament from the Likud Party, called for Portman’s Israeli citizenship to be stripped.

But Portman soon clarified that her action was targeted at Israeli leadership, not the state of Israel as a whole.

“I chose not to attend because I did not want to appear as endorsing Benjamin Netanyahu, who was to be giving a speech at the ceremony. By the same token, I am not part of the BDS movement and do not endorse it,” Portman wrote in a statement on Instagram. “Like many Israelis and Jews around the world, I can be critical of the leadership in Israel without wanting to boycott the entire nation.”

BDS supporters hope hurting Israel’s economy will change Israeli policy

Israel has a strong economy, a large part of which is driven by a booming tech sector that houses a number of premier Western tech firms. It’s difficult to see how even a massive surge in BDS campaigns could destroy that reality. And so far, BDS’s successes haven’t prevented Israel from seeing a steep increase in foreign investment in recent years.

But the country’s biggest concern is similar to that of Israeli businesses being targeted by BDS — the cost to its reputation.

“It’s not just an impact of dollars and cents, but it’s an impact that is psychological as well,” Yousef Munayyer, executive director of the US Campaign for Palestinian Rights, told me in an interview in 2016. “It’s about the effect of knowing that there are costs in the form of international isolation to continuing down the road Israel is on.”

Israeli leaders are deeply concerned that an uptick in successful BDS campaigns and increased enforcement of EU guidelines would isolate it in the global arena. That’s why politicians from across the political spectrum in Israel have begun to describe BDS as an existential threat in recent years, and argue that its chief goal is “delegitimization.”

For both critics and supporters of the BDS movement, that level of Israeli concern may be the clearest evidence that the campaign is picking up momentum. Whether it will be able to change Israeli policy is a different question entirely.