In 1947 the National Bloc split into two competing parties, the National Party and the People's Party. Al-Haffar joined the National Party and became its secretary-general. He served as deputy to Prime Minister Mardam Bey until the military coup of Chief of Staff Husni al-Za'im overthrew the Quwatli administration. Al-Haffar was arrested along with most of Quwatli's allies. He was released after direct interference by former Lebanese Prime Minister Abdul Hamid Karami.