At last week’s congressional hearing on the Secret Service and the assassination attempt against former President Donald Trump, Rep. Raja Krishnamoorthi asked: “What can Congress actually do to stop this from happening again?”The congressman, a Democrat from Illinois, then showed the chamber a graphic on political violence that was published a month ago by the Chicago Project on Security and Threats, which I lead.The graphic shows that 74% of Americans want members of Congress to come together to denounce all political violence. This stance crosses party lines, with 86% of Democrats, 51% of independents and 70% of Republicans saying so.While individual members of Congress have made statements denouncing the Trump assassination attempt, Krishnamoorthi challenged the entire House of Representatives to go much further, proposing a resolution in the near future “condemning any political violence in America” and calling for support from every member of the chamber. Such resolutions go to the House for a vote and are not signed into law, but they convey a message — especially when they pass unanimously.After last week’s grueling hearing, the head of the Secret Service resigned, writing to her staff: “I take full responsibility for the security lapse.” That departure will not prevent future bloodshed. However, Congress has a chance to do so.At this critical time, members of Congress — both Republicans and Democrats — must stand together to oppose political violence. The Trump shooting is only the latest of a growing string of incidents. Indeed, we are seeing the most violent era in American politics in decades, and now is certainly the time for all political leaders at all levels of government — national, state and local — to adopt similar resolutions and make similar unified statements.Political violence in the United States is entering a new stage as America faces mounting domestic terrorism: violent anti-government and other political actions by militias, small groups and volatile individuals within the United States.To be sure, famous acts of domestic terrorism occurred from the 1990s through 2010, including the violent standoff at Ruby Ridge in 1992, the Oklahoma City bombing in 1995, the violent protests against the World Trade Organization meeting in Seattle in 1999, and the multiple arsons and bombings conducted by individuals affiliated with the Earth Liberation Front and Animal Liberation Front from 1995 to 2010.What’s happening now is different. Political violence in America is escalating, both in number and in kinds of violent ...