He took part in establishment of the Croatian People's Progressive Party in 1904 and influenced its accession to the Croat-Serb Coalition.
Following 1927, he became a political ally of the Croatian Peasant Party leadership within the framework of the Peasant-Democratic Coalition [hr].
Wilder was among signatories of 1932 Zagreb Points resolution condemning Serbian hegemony within the Yugoslavia.
After the outbreak of the World War II and Invasion of Yugoslavia, Wilder left the country and settled in London.
In the United Kingdom, Wilder provided commentary for BBC Radio condemning Ustaše-led puppet state of the Independent State of Croatia as well as accusing Archbishop of Zagreb Alojzije Stepinac of collaborating with the Axis powers.