MOVEMENTS MATTER. In 1980, ship workers in the Polish city of Gdańsk went on strike, demonstrating for independent unions, better conditions, and political reforms. Poland, which had been under Soviet influence since World War II, was facing an economic crisis with food shortages, inflation, and poor working conditions that led to growing unrest among workers. The communist government in the country suppressed dissent and sought to control labor unions. Under the trade unionist Lech Wałęsa, the Polish Solidarity Movement was born.
It became one of the largest and most successful mass movements of the 20th century. Within months, it had grown to 10 million members, about a third of the Polish workforce, bringing together workers, intellectuals, Catholics, and anti-communist dissidents. Despite government crackdowns, the movement persisted, leading to talks in 1989 that resulted in semi-free elections and the legalization of Solidarity as a political party. That year, Solidarity won enough parliamentary seats to lead the government. The following year, communism ended in Poland, and in 1990 Wałęsa—who went on to win a Nobel Peace Prize—became president. Solidarity inspired democratic movements in Hungary and the former Czechoslovakia and East Germany and helped catalyze the collapse of the Soviet Union.
What does it take for a social movement to succeed? What factors led to the Polish Solidarity Movement gaining such widespread traction? A Kennedy School faculty member has conducted pioneering work to crack the code behind successful movements like Solidarity.
Erica Chenoweth, the Frank Stanton Professor of the First Amendment and HKS academic dean for faculty development, is an expert in nonviolent civil resistance.
In “Why Civil Resistance Works: The Strategic Logic of Nonviolent Conflict” (2011), Chenoweth and co-author Maria Stephan share the results of their research. They found that successful nonviolent resistance needs a diverse group of participants sustained over time who can create loyalty shifts among regime supporters and a creative range of protest tactics that can withstand direct repression without resorting to violence.
Chenoweth developed the “3.5% rule”: the observation that most successful movements tend to have mobilized at least this percentage of a population. Chenoweth explains that if that many people are actively involved in a resistance movement, a high proportion of the population is likely to be sympathetic to, or supportive of, the resistance movement. In a 2020 discussion paper, Chenoweth clarifies that this number is a tendency rather than an ironclad law: “The 3.5% participation metric may be useful as a rule of thumb in most cases; however, other factors—momentum, organization, strategic leadership, and sustainability—are likely as important as large-scale participation in achieving movement success and are often precursors to achieving 3.5% participation.”
Chenoweth is also one of the scholars behind the Crowd Counting Consortium (CCC), which documents protests and demonstrations in the United States to measure the effectiveness of civil resistance. Policymakers and journalists have used CCC data to evaluate public sentiment, social movement energy, and regional political dynamics. Its database serves as a fact-checking tool against misinformation about protest size or violence. For example, the consortium has found that, since January 2017, when it first started counting demonstrations and their crowd sizes, the current pro-Palestine wave has accounted for the largest, most sustained U.S. protests sparked by a foreign event. CCC has also helped quantify the scale and spread of protests such as the Women’s March in 2017 and the George Floyd protests in 2020, offering insight into the extent to which those were nonviolent resistance movements.
This year’s anti-Trump “Hands Off” and “No Kings” protests rank among the largest in the country’s history. Chenoweth’s team has collected data showing that the anti-Trump protests in 2025 have been larger than those in 2017. Their estimates suggest that from 2 million to 4.8 million people participated in more than 2,150 No Kings demonstrations nationwide on June 14—numbers comparable to participants in the 2017 Women’s March, but across far more locations in the country. The team found that those protests were remarkably peaceful—counter to some claims and depictions.
The CCC’s analysis of protests, the 3.5% rule, and other work have provided insight for movement organizers along with scholars and policymakers who want to evaluate and understand social movements in the United States and around the world.
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From political prisoner to pro-democracy researcher
IN HIS HOME COUNTRY Venezuela, Freddy Guevera MC/MPA 2024 was imprisoned and then exiled for his political advocacy. As a student, he helped lead pro-democracy protests in the face of an increasingly authoritarian government. He later co-founded the progressive party in Venezuela and won a seat in his country’s Congress, before political persecution led to nearly three years in hiding in the Chilean embassy, imprisonment, and exile.
Guevera is a Democracy Visiting Fellow at the Ash Center for Democratic Governance and Innovation and has worked with Professor Erica Chenoweth as a research fellow at the Nonviolent Action Lab, where he has studied why pro-democracy movements in countries around the world have failed—and how such movements might succeed. At the lab, he is working on a global knowledge network to promote cross-collaboration between activists, scholars, and practitioners; updating the counter-autocracy strategic framework; and learning from global lessons of democratic backsliding. In an HKS graduating student profile in 2024, Guevera said, “My commitment is not only to Venezuela. It’s to democracy itself—and how I can help and contribute to this global struggle.”
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Banner image: Aerial view of demonstrators marching in Colombia; Photo by Jimmy Villalta/VWPics/AP Images
Inline image: Freddy Guevera MC/MPA 2024, who was a prominent opposition leader in Venezuela, speaks to reporters. Photo by Jaime Saldarriaga/AFP/Getty Images
Faculty portrait by Martha Stewart