Gentleman Joe Palooka (movie, 1946)

In the second film of Monogram's Joe Palooka series, Joe is 'used', by two state senators scheming to obtain oil-rich lands, in a publicity campaign to get the land transferred to the state, supposedly for a park. When Joe learns that he has been used as a dupe he becomes disillusioned and leaves the prize=fighting profession. But, his manager, sparring partners, and fiancée manage to expose the land-grab scheme, clear Joe's name and discredit the crooked politicians.