For Dictatorship, the second answer is incomplete, a dictator may obtain power not only through elections but by a military or institutional coup d'état, a civil war or a military intervention by a foreign power.
In a republic, power is held by those citizens that are able and government is a public matter (res publica in latin) to vote and the power comes from their vote during elections.
It was the belief that it was destiny for the Caucasians to expand and to take over North America. This caused conflicts when the Caucasians wanted to take land from the native Americans.
