GOTEBORG, Sweden — Three decades after Prime Minister Olof Palme was gunned down on a Stockholm street, his unsolved killing continues to reverberate through Swedish politics and society.

In the prelude to the 30th anniversary of the shooting on Sunday, news organizations are recounting a range of theories about the identity and possible motivation of the killer, including that the crime had been committed by an unemployed Swede with a grudge, or by an American acting on orders from the Pinochet government in Chile. One tabloid published a list of items this week to help younger readers understand the leader “who put Sweden on the world map.”

The continued fascination with Mr. Palme stems in part from the mysteries surrounding his death — he was shot as he and his wife, Lisbet, walked home without bodyguards from a movie on a Friday night — and in part from his legacy as the embodiment of left-leaning values that once seemed to define his country: commitment to a robust welfare state at home and a foreign policy driven by moral considerations.