Our family knows the cost of political violence. Senators must show profiles in courage.

William Kennedy Smith, a physician, and Kathleen Kennedy Townsend, executive director of Retirement Security for All, are the nephew and niece of President John F. Kennedy and the nephew and daughter of Sen. Robert F. Kennedy.

In 2016, Ambassador Jean Kennedy Smith, the last of the nine children of our grandparents Joe and Rose Kennedy, co-wrote an op-ed with one of us that ran in The Washington Post, entitled “Political violence is no joke.” Written in response to inflammatory rhetoric by then-candidate Donald Trump, it read in part, “Political violence...