Tragedy in Dallas
The assassination of President John Kennedy on November 22, 1963 occurred so quickly and shockingly that questions of whether Vice President Lyndon Johnson should act as President were never really considered. In its aftermath however, questions of presidential disability and succession took center stage in a way, and with an urgency, which had previously never been the case.
This was largely due to Johnson himself. Six years prior to being sworn in as Vice President, the then-Senator from Texas suffered a near fatal heart attack, and though only in his mid-50's, Johnson was unusually self-aware about his own health and mortality.
In the wake of the Kennedy assassination, the already shocked nation would be further alarmed five days later as Lyndon Johnson would address Congress. The reason was the appearance on television of the two men next in the line of succession should Johnson die - House Speaker John McCormack looked an unusually old 71, while Senate President Pro Tem Carl Hayden looked almost every day of his 85 years. The thought of either of these two being one Lyndon Johnson heartbeat away from running the country was seen as all too concerning in the nuclear age.
The issue would temporarily be laid to rest a year later, as Johnson was elected to a term as President in his own right along with Minnesota Senator and Vice Presidential nominee Hubert H. Humphrey, Jr. But unlike past attempts to address presidential succession and disability that withered as memories of an averted succession crisis passed over time, one young Senator from Indiana (with Johnson's help) would put the matter to rest once and for all.