What’s Causing the Rise in Left-Wing Incidents?
The increase in left-wing incidents in the past decade is driven by plots and attacks directed at government and law enforcement targets. Of the 41 left-wing incidents since 2016, anti-government extremism motivated 17 of them, and partisan extremism motivated another 11. All left-wing attacks through July 4, 2025, appeared to be motivated by one of these ideologies, and the Kirk killing fits this pattern, although details about Kirk’s alleged killer are still emerging.3
The only significant break from this trend was a surge of six left-wing firebombings against pro-life targets (pregnancy crisis centers and the office of an anti-abortion group) in the summer of 2022 around the time of the overturning of Roe v. Wade. These attacks were intentionally perpetrated at night against unoccupied buildings to reduce (though not eliminate) the risk to people.
To understand rising left-wing violence, it is useful to distinguish between partisan extremism and anti-government extremism.
Partisan extremism includes attacks and plots against elected officials, political candidates, political party officials, and political staff and workers from terrorists with opposing political views. For example, on January 28, 2025, U.S. Capitol Police arrested Riley Jane English, a 24-year-old from Massachusetts, on the National Mall in Washington, D.C., after she approached officers and revealed she was carrying a folding knife, two Molotov cocktails, and a lighter. According to prosecutors, English said she intended to kill senior U.S. officials, initially identifying Defense Secretary Pete Hegseth, whom she described as a “Nazi,” before shifting her focus to House Speaker Mike Johnson and then to Treasury Secretary Scott Bessent. She also expressed a desire to attack the conservative Heritage Foundation.4
In a separate incident on March 30, 2025, an assailant set fire to the headquarters of the Republican Party of New Mexico in Albuquerque, igniting the entrance late at night. Graffiti reading “ICE = KKK” was spray-painted on a wall near the site.5
Attacks such as English’s plot to assassinate senior officials and the arson of the Republican Party’s New Mexico headquarters reflects the most severe effects of polarization in the United States. A variety of survey data underscores that this issue is widespread and worsening. In 2016, fewer than half of Republicans or Democrats described the opposing side as immoral, dishonest, or unintelligent. By 2022, however, most Republicans described Democrats as immoral (72 percent), dishonest (63 percent), and unintelligent (70 percent), while most Democrats said the same of Republicans (64 percent, 61 percent, and 52 percent, respectively).6
Similarly, while less than 4 percent of Americans express support for partisan violence such as assault, arson, or murder, both sides greatly overestimate their opponent’s willingness to endorse such actions, with Democrats believing 45.5 percent of Republicans support partisan murder, and Republicans believing that 42 percent of Democrats do.7
Although the vast majority of Americans would never commit partisan violence and oppose it, widespread polarization and misperceptions that the other side is far more violent than it actually is creates a dangerous environment where extremists can more easily rationalize using violence. Growth in even a tiny minority who are willing to commit partisan violence has the potential for tremendous consequences considering the combustible political climate in the United States and the fact that symbolic and strategically important political leaders are among the potential targets.
In addition to partisan extremism, anti-government extremism has also become more pronounced as a motive for left-wing attacks in 2025, particularly around the issue of immigration.
In one incident on July 4, 2025, a group attacked the U.S. Immigration and Customs Enforcement (ICE) Prairieland Detention Facility in Alvarado, Texas. According to federal prosecutors and law enforcement statements, approximately a dozen individuals dressed in black clothing and equipped with tactical gear initiated the attack by detonating fireworks and spray-painting anti-ICE graffiti on vehicles and structures outside the facility.8 When an Alvarado police officer responded to the scene, an assailant positioned in a nearby wooded area opened fire, wounding the officer in the neck.9 Meanwhile, another individual reportedly fired 20 to 30 live rounds at unarmed ICE correctional officers outside the facility.10 Law enforcement subsequently apprehended 14 suspects, who now face federal charges including attempted murder of federal officers and firearm-related offenses.11 Searches uncovered AR-style rifles, a pistol, body armor, two-way radios, spray paint, and flyers with anti-ICE slogans.12 One of the alleged attackers stored cellphones inside Faraday bags, which are used to block signals and indicate premeditated efforts to evade law enforcement tracking.13
Traditionally, anti-government extremism refers to violence aimed at state institutions viewed as illegitimate or oppressive, whereas partisan extremism targets specific political figures or individuals based on party affiliation. As events such as the Prairieland ICE attack suggest, left-wing opposition to the Trump administration in 2025 often manifests as both: rejecting its political leadership and resisting its efforts to expand the authority of military and law enforcement institutions. Together, partisan and anti-government extremism help explain why 2025 has seen an escalation of left-wing violence, as opposition to the Trump administration fuels attacks against both its political leadership and the state institutions that carry out its agenda.
Left-Wing Weaknesses
Despite the rise in the number of left-wing terrorist incidents, there exist several characteristics and conditions that limit the scale and sophistication of attacks. The overall low lethality rates in left-wing attacks are probably attributable to several factors, including target selection, target scope, tactical methods employed, low levels of perpetrator skill, and counterterrorism measures.
First, left-wing perpetrators typically select targets that limit opportunities for mass killing. In the past decade, left-wing attacks most commonly occurred at government or law enforcement facilities. These locations are often protected by physical fortifications and security personnel, making it more difficult for perpetrators to kill targets during an attack. For example, in the July 2025 attack on ICE’s Prairieland Detention Facility, one police officer was wounded before additional law enforcement forced the attackers to flee.14 The attackers’ choice of a hardened federal compound with security personnel on site contributed to the attack’s failure to kill any victims. This contrasts with jihadist attacks, which most commonly target crowded public areas with limited or no security measures, such as the car ramming attack on Bourbon Street in New Orleans on January 1, 2025, that killed 14 victims.
Second, left-wing violence is often narrowly directed at specific individuals rather than indiscriminate killings of civilians. Most notably, 10 of the 13 victim fatalities from left-wing attacks in the past decade have been police officers ambushed in public areas by attackers using firearms. This pattern underscores that even the deadliest left-wing attacks have tended to focus on targeted confrontations with law enforcement rather than mass-casualty events.
Third, left-wing perpetrators frequently employ tactical methods poorly suited to producing mass casualties. In the past decade, 20 of 35 left-wing attacks have involved the use of incendiaries or arson as the primary weapon. Incendiaries and acts of arson typically lack precision, resulting in damage that can be severe but not necessarily lethal. In some cases, the arson was done at night, which further reduced the likelihood of fatalities because the targets were often sites that were largely unoccupied.
Taken together, the typical target selection, scope, and weapon selection of left-wing attackers reflect an intent to signal opposition or cause disruption rather than inflict mass casualties.
Fourth, left-wing perpetrators frequently lack the weapons and tactical training to maximize their impact. For example, on February 14, 2022, Quintez Brown, a 21-year-old black nationalist, entered the Louisville campaign office of Democratic mayoral candidate Craig Greenberg with a 9 mm pistol. Prosecutors argued that Brown saw himself as an “equalizer” striking at a symbol of gentrification and oppression.15 Despite firing multiple rounds at point-blank range, Brown missed his target, with one bullet only grazing Greenberg’s sweater.
Fifth, unlike many foreign terrorist organizations with centralized leadership, funding, and training infrastructures, left-wing terrorists, like most terrorist actors in the United States, operate as loosely affiliated networks or as lone individuals, limiting their ability to train and to plan and execute complex operations. Social and technological factors, including online radicalization, often result in isolated actors lacking the resources, expertise, or coordination needed for sophisticated attacks.
The lack of organization also creates a multiplicity of competing goals that hinders strategic effectiveness. Like their right-wing counterparts, left-wing terrorists are against many things, and there is no clear prioritization of targets within the movement. Similarly, they are unable to calibrate violence, making it more likely to backfire.
Sixth and finally, U.S. law enforcement and intelligence agencies have developed robust counterterrorism measures, particularly since 9/11, that disrupt plots and largely deter large-scale attack planning across all ideologies. Legal restrictions, such as controls on explosives and surveillance of known extremist networks, further constrain terrorist operational capacity. Social media, in addition to enabling radicalization, also hinders operational security, revealing intentions and possible actions of individuals who, in the past, might have remained undetected. Combined, these dynamics help ensure that, while the threat of terrorism remains, the capacity of all U.S.-based terrorist movements to execute attacks is significantly diminished.
Why Have Jihadists and Right-Wing Incidents Fallen?
Explaining non-events, such as why attacks from rival ideological groups and individuals have fallen, is always difficult, but there are several possible reasons for the decline in jihadist and right-wing terrorism.
For jihadists, the main foreign terrorist groups in recent years—al Qaeda and the Islamic State—are far weaker than they were at their peaks. The United States and its allies have killed group leaders, often leaving them in disarray. Al Qaeda, for example, still has not named a successor since the death of Ayman al-Zawahiri in 2022. The Islamic State likewise has lost numerous leaders, and it no longer has an above-ground caliphate where it can train people. In both cases, the losses have made the group less inspiring, although some bottom-up radicalization remains a concern. Finally, factors like aggressive law enforcement and a U.S. Muslim community that collaborates with law enforcement lead many would-be attackers to be caught in early stages of plotting.16
The sudden decline in right-wing terrorism is both more striking and harder to explain. From 1994 through 2000, there was an average of 21 right-wing attacks or plots each year. In the following decade, right-wing incidents fell to an average of 7 annually. From 2011 through 2024, right-wing incidents climbed back up to an average of 20 a year. In the first half of 2025, however, there was only one right-wing terrorist incident in the United States—the killing of Minnesota state legislator Melissa Hortman and her husband in June—a remarkable drop off.
Aggressive law enforcement efforts under former President Biden hurt the right-wing extremist movement, with the January 6 investigation in particular causing disarray.17 The U.S. government brought charges against over 1,000 individuals, including many leaders of groups like the Oath Keepers and Proud Boys. In addition, like left-wing terrorism, right-wing terrorism is highly decentralized, and the vast majority of the most lethal attacks in the last 10 years have been perpetrated by lone actors linked to various networks but not tied to any group.
Trump’s election, however, appears to have changed the threat. Although it is impossible to definitively prove the link between the policies of and positions championed in Trump’s second term and the decline in right-wing terrorism incidents in the United States, it is probable that at least some extremists do not feel the need to act violently if their concerns are being addressed.
Most notably, the administration has aggressively targeted immigrants, with high-profile efforts to identify, detain, and deport them. Anti-immigrant sentiment is one of the most important violent extremist motivations in recent years. The Trump administration has also warned of “deep state” abuses, criticized and abolished programs involving diversity, promoted some conspiracy theories, and hired individuals who openly embraced white supremacy.18 In addition, Trump’s victory temporarily ended many concerns about a Democrat-orchestrated “stolen election,” a leading conspiracy that motivated many extremists in the past.19 Enrique Tarrio, the former Proud Boys leader and a convicted seditionist whom Trump pardoned, recently summed up the president’s potential psychological effect on the violent far right: “Honestly, what do we have to complain about these days?”20
At the same time, it is important to stress that correlation does not mean direct causation. The administration’s rhetoric and policies may overlap with themes found in extremist discourse, but that does not necessarily imply intent to encourage violence. Rather, extremist actors may perceive mainstream political validation of their grievances as reducing the need for independent mobilization or, more concerningly, as tacit endorsement of their worldview in situations where the administration faces resistance or does go far enough in the eyes of an extremist.
What Is to Be Done?
The best responses to the Kirk killing and political violence from any source involve few theatrics but can be highly effective.
First, the government should avoid overreacting with crackdowns on peaceful organizations, which will serve to strengthen extremist views. Radicals will argue that peaceful politics will inevitably fail and that only violence will make a difference. In response to the Kirk killing, President Trump warned that a “radical left group of lunatics” are engaged in a campaign of violence.21 Other conservative voices, from members of Congress to online influencers, have similarly claimed that the left is engaged in “war.”22 Kirk’s shooter appears to have acted alone, but Trump has claimed that a network of political organizations fund and support violence, and must be neutralized—a threat that, if acted on, could lead to government action against an array of non-violent organizations whose political positions were anti-Kirk and are anti-Trump.23 These actions will be counterproductive for combatting terrorist threats.
Second, it is important to resource all dimensions of the terrorism threat. Left-wing terrorism is a Trump administration priority, but jihadist terrorism also remains a concern even though it has declined. Right-wing terrorism could come roaring back, especially if in 2028 there are complaints of a “stolen election” or similar incendiary claims. Developing the programs and expertise to suppress different forms of terrorism takes years, and ignoring a long-term threat to go after a more immediate one could be deadly over time.
Finally, although leaders are not responsible for extremists in their midst, they are responsible for how they behave toward extremists. U.S. political leaders and activists need to lead by condemning violence on their side and calling for calm when it involves violence on the other side. The American Muslim response to jihadist terrorism offers a useful model. Muslim leaders came together to repeatedly condemn jihadist violence, and this reduces the appeal of terrorism.24 When the mainstream condemns an attack, the individual is less likely to be seen, and see themselves, as a hero or successful agitator, and the community as a whole is more likely to work with law enforcement.
Many leading Democrats have vehemently condemned the Kirk shooting.25 For their part, many prominent Republicans also immediately condemned right-wing attacks in recent years, including the assassination of Hortman earlier this year and the attack on Paul Pelosi in 2022.26 But the track record is far from perfect. The celebrations among some on the left of Luigi Mangione is a failure to undermine support for left-wing violence.27 Similarly, the failure of some conservative leaders to condemn white supremacists and other violent extremists is a major problem, allowing these extremists to believe they are carrying out the will of a broader political movement.28
Utah Governor Spencer Cox has served as a model in unequivocally denouncing extremists. Cox described Kirk’s killing as “an attack on all of us.”29 And he offered a simple exhortation that would benefit both sides, particularly in moments like these, when violence can spiral: “Disagree better.”30
Daniel Byman is the director of the Warfare, Irregular Threats, and Terrorism Program at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Riley McCabe is an associate fellow for the Warfare, Irregular Threats, and Terrorism Program at CSIS.
This report is made possible by general support to CSIS. No direct sponsorship contributed to this report.