Robert F Kennedy Sr., brother of President John Fitzgerald Kennedy Sr.. He was expected to be the next president after JFK, then later he was seen as likely to be the next president after Lyndon B. Johnson. He was assassinated during the democratic primaries, in which he was the primary anti Vietnam war/pro civil rights candidate.

Johnson remains the last president to oversee major expansion of infrastructure and welfare. Biden tried for the infrastructure, but it was largely repairing as opposed to Johnson doing The Great Society which included everything from the civil rights act and extending constitutional protections to native reservations to Medicare and Medicaid to funding metro rail in several major cities and so much more. Kennedy likely would have continued down this path but with much less killing south east Asians