Traditionally the Norwegian kings had been elected by the several things held around the country.
After the civil wars in the 12th century, Erling Skakke introduced a new law that there would be only one king, and that the oldest surviving son of the previous king should inherit the throne.
During the reign of Inge II there was never any clear heir, and after his death several relatives claimed the throne.
Norway became an elected kingdom, and joined several unions with Sweden and Denmark.
However, the tradition arose that during his own lifetime the King would choose an heir among his sons and have him hailed as such, strongly influencing the electing council's choice.