After the creation of the new constitution Serpa continued as President of Liberal Directorate in Santander Department and President of the Central Politics Commission of the Liberal Party. He was then prospect for presidential candidate in 1998, but was shaded by Ernesto Samper. Serpa was then elected National Director of the Liberal party for the period 1998 to 1999. During the government of Álvaro Uribe, Serpa was appointed ambassador of Colombia to the Organization of American States (OAS) and he also disputed the presidential bids of 2002 and 2006.