 The U.S. Constitution, including both the presidential line of succession and the 25th Amendment, dictates what happens when a president is incapacitated.The Speaker of the House (at the time, Tip O'Neill, Democrat) and the president pro tempore of the Senate (at the time, Strom Thurmond, Republican), precede the secretary of state in the line of succession.Haig later clarified,

In April 1982 Haig conducted shuttle diplomacy between the governments of Argentina in Buenos Aires and the United Kingdom in London after Argentina invaded the Falkland Islands.