Turk 182! (1985)

"Who said you can't fight City Hall?"

After New York City firefighter Terry Lynch is unable to receive any compensation for an injury incurred during the off-duty rescue of a young girl, he grows suicidal. Furious, his brother Jimmy attempts to have Mayor Tyler intervene, but the corrupt politician instead denounces Terry as a drunk. Determined to get justice, Jimmy begins a graffiti campaign of embarrassing slogans mocking the mayor, which soon captivates the city.