In 1978 Haacke became politically involved and joined the newly founded Democratic Turnhalle Alliance (DTA). In the 1979 National Assembly election he became a member of the Constituent Assembly. He served as the Minister of Water Affairs from 1979 to 1980. In 1980 he left the DTA after the DTA participated in the first-ever universal suffrage election in South West Africa, which was widely regarded as fraudulent and aimed at establishing a puppet state by South Africa.
Haacke subsequently joined the more oppositional Namibia National Front (NNF) where he became secretary-general in 1982. In 1983 he went into exile in London, where he worked as the NNF representative for eight years. In 1991 Haacke returned to Namibia.
In 1994 he rejoined the DTA, from which he split again four years later because he was dissatisfied with its leadership. He then formed his own political party, the Monitor Action Group (MAG). Haacke was the presidential candidate of the MAG in the 1999 presidential election, but got less than 1% of the vote. In the 2004 parliamentary elections, he stood at number 1 on the MAG candidate list, but the party won no seats. He stood again in the 2009 elections, but this time at number 13. Again the MAG won no seats. He retired from active politics in 2009.
Haacke is a prominent campaigner for animal welfare and an advocate for the introduction of a hunting and game ranching bill. In July 2009, he filed a High Court case in which he challenged the constitutionality of the Namibian government's policy of issuing permits to hunt trophy and game animals. The case received international attention.