Long before Secretary of State Alexander Haig assured the nation that he was in control during the crisis period following the 1981 shooting of President Ronald Reagan, members of the Senate had tried to block that cabinet officer's chances of temporarily assuming the duties of the presidency.
The framers of the Constitution had left Congress with considerable responsibility for resolving questions about the new government's structure and operations. Considering the high rates of serious illness and early death in late eighteenth-century America, one of the most pressing among those questions was, "Who would become president if both the president and vice president died or were otherwise unavailable to serve during their terms of office?" The Constitution provides only that Congress may pass a law "declaring what Officer shall then act as President."
In 1791, a House committee recommended that this duty fall to the cabinet's senior member—the Secretary of State. Federalist senators objected because they had no desire to see Secretary of State Thomas Jefferson, leader of the growing Antifederalist opposition, placed so close to the presidency. Others proposed the Senate's president pro tempore, reasoning that as this official succeeded the vice president in presiding over the Senate, he should also succeed the vice president in performing the duties of the presidency. This plan attracted opposition from those who assumed the president pro tempore would remain a senator while temporarily performing duties of the presidency and feared the arrangement would upset the balance of powers between the two branches. Others suggested the Chief Justice of the United States or the Speaker of the House of Representatives. At an impasse, Congress adjourned for nine months, thereby risking governmental paralysis in the event of presidential and vice-presidential vacancies.
Early in the Second Congress, on February 20, 1792, the Senate joined the House in passing the Presidential Succession Act—a compromise measure that placed in the line of succession its president pro tempore, followed by the House Speaker.
Years later, in 1886, Congress responded to longstanding uneasiness with this arrangement by removing its two officers from the line of succession and substituting the president's cabinet members, by rank, beginning with the Secretary of State. This troublesome issue received yet another revision in 1947, when Congress inserted the Speaker of the House and Senate president pro tempore, in that order, ahead of the president's cabinet.
Feerick, John D. From Falling Hands: The Story of Presidential Succession. New York: Fordham University Press, 1965.