 After working for some time on projects for the Christian Democratic Appeal, Eerdmans worked at the Ministry of Justice from 1997 until 1999.In 1999 he became secretary to Ivo Opstelten, the mayor of Rotterdam.In 2002 Eerdmans contacted Pim Fortuyn, who at that time was busy assembling a list of candidates for his new political party, Pim Fortuyn List (LPF).