The market is always downstream from politics. Karl Marx famously used the term political economy to reference both political and economic forces, because neither is coherent without the other.
Political economy as an area of inquiry took off in the late 18th century--in no small part due to Adam Smith--and was already very well established before Marx was born [1]. Absent evidence to the contrary it seems questionable to assert that Marx's use of the term was anything other than the common use of the time.
[1] https://books.google.com/ngrams/graph?content=political+econ...