If the President resigns or dies while in office, the successor is determined by the presidential line of succession, as specified by the United States Constitution and the Presidential Succession Act.
United States | United Kingdom | Republican Party (United States) | Democratic Party (United States) | United States House of Representatives | President of the United States | United Nations | United States Senate | United States Navy | United States Army | Supreme Court of the United States | United States Air Force | Native Americans in the United States | United States Congress | Parliament of the United Kingdom | 66th United States Congress | Prime Minister of the United Kingdom | 74th United States Congress | 18th United States Congress | 73rd United States Congress | 54th United States Congress | 61st United States Congress | United States Marine Corps | United States Department of Defense | 64th United States Congress | 65th United States Congress | 53rd United States Congress | 52nd United States Congress | 55th United States Congress | United States Army Corps of Engineers |
In the United States the ranking of members of the Cabinet forms a part of the presidential line of succession.
In the case of an attack on Washington, the president or the presidential successor along with any potential surviving members of Congress, military leadership, department and agency heads, and Supreme Court justices would be high-value rescue targets.