In 1973 Hartling became Prime Minister of Denmark when the sitting Danish Social Democratic Party government of Anker Jørgensen was unable to form a government after the 1973 Danish parliamentary election.
Pada 1973, Hartling menjadi Perdana Menteri Denmark saat mendududki pemerintahan Partai Demokrat Sosial Denmark Anker Jørgensen yang belum membentuk pemerintahan setelah pemilihan parlementer Denmark 1973.