A new era of political violence is taking hold in America / How violence became a theme of America's election / The U.S. has had a long history of political violence, but experts see a new trend / Rep. Lisa Blunt Rochester on U.S. political violence / Political violence becomes America's new norm - but is still shocking / How Americans Justify Political Violence / Comparing the history of political violence in America and the UK / Violence plagued all levels of American politics long before the attempt on Trump's life / 'Political violence in the US is linked to a history of conquest and predation' / Despite appeals for peace, the U.S. has a long history of political violence