On 8 April 1989, the Progressive Federal Party, Independent Party, the National Democratic Movement and the Fourth Force of 'Ontevrede Afrikaners' (Dissatisfied Afrikaners) resulted in the formation of the Democratic Party in Johannesburg. The organisation was reformed as the Democratic Alliance (DA) in 2000, when the Democratic Party and the New National Party signed an agreement to form the party. The Democratic Alliance still advocates the same policies of non-racialism, and retains the constitution drawn up by members of the Progressive Party in 1959, the forerunner of the Democratic Party which was led by Helen Suzman. The Democratic Party therefore played an important role in the negotiations leading to the adoption of an Interim Constitution during and after 1990, as then DP leader Zach de Beer was elected the first Management Committee Chairman process of CODESA (Convention on a Democratic South Africa).  
References

Democratic Alliance,"Our History",From: Democratic Alliance,[Online],available at: www.da.org.za,[Accessed at: 04 April 2014]|Wallis, F. (2000) >Nuusdagboek: feite en fratse oor 1000 jaar. Kaapstad : Human & Rousseau.)