Article IV · Section 4 of 4
What the nation promises the states
Article IV: The states
The one-line version
The nation promises each state an elected government and protection from invasion.
Section 4 in plain English
The United States promises every state a "Republican Form of Government," meaning a government run by elected representatives. It must protect each state from invasion.
If a state's legislature asks, the United States must also help stop violence inside that state. The governor can ask if the legislature cannot meet.
Original text, 1788
The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.