Pasted on almost every tree and pole the posters were intended for political campaigning and for acquaintingthe voters with the candidate.

Note: If you intend that your sentence refers to "posters" for many candidates, not just one, you'd also need to revise that part to show plural: Pasted on almost every tree and pole the posters were intended for political campaigning and for acquainting the voters with the candidates.

The plural would balance a second set of parallelism: posters; voters; candidates.... and ... campaigning; acquainting.