When a gunman opened fire on former President Donald Trump this summer in Butler, Pennsylvania, it was a first for many Americans who had never seen an attempted assassination on a major political figure in this country.But threats and violence against political candidates and their supporters have been surging in recent years. Homeland Security officials warned recently that the nation's threat environment is expected to remain high over the next year, in part because of the 2024 election cycle.RELATED STORY | Scripps News exclusive: US Capitol Police chief confident agency is prepared for potential election violenceFor the past several months, Scripps News has been digging into this troubling trend. We've uncovered cases where people have been sent to prison for making threats, and others where people have ended up in the hospital as victims.We sift through dozens of cases, police reports, body camera footage and court documents, and talk to the people in power whose job it is to safeguard democracy to understand where the risk of political violence comes from and how it's changed.