I know approximately one gazzillion songs written for political purposes. Most of them aren't very good songs, though. There are threads about Joe Hill, and threads about Jacobite Ballads, on Mudcat, and then there are a lot of union songs. Try

Shall we still be slaves and work for wages?
It is outrageous!
Has been for ages!
The world by right, belongs to toilers,
And not to spoilers of liberty!

or,

Grover, Grover, four more years of Grover!
In we'll go, out they'll go, then we'll be in clover!

or,

The Democratic Party is for you and you and you!
The Party of the many and not just for a few!
From the city and the country for the big ones and the small,
Oh! the Democratic Party is the only one for all!
From the East and West, from North and South they come,
Singin' the Donkey Serenade,
Come on and beat your drum-de-um-drum
We'll march along together, and on election day,
We're voting Democratic, 'cause we're voting for the U.S.A-ay-ay!

Wait, it gets even worse................