Following the 1976 Montejurra shootout the self-governmental statement condemned violence and declared it should never happen again. Few months later Marco successfully opposed the motion aimed at democratisation of the regional regime. In the Cortes he remained inactive and was mostly witness to the debate on Ley para la Reforma Política; during the final vote on November 18, 1976, he decided to support the project, thus opening the way for further reform; some name the act as "suicide of the Francoist Cortes". Afterwards and in name of the Diputación he sent congratulations message to the prime minister Adolfo Suárez. In early 1977 Marco was among co-founders of Alianza Foral Navarra, a right-wing party focused on Navarrese identity by some scholars categorized as the post-Francoist “bunker”, and became its president. The organisation demanded restoration of traditional Navarrese establishments and sponsored similar declaration of the Diputación, against a competitive project favored by UCD; during general elections AFN garnered 8,5% of the votes in Navarre and was the 4th political force in the province.