There are not a lot of books with political cartoons in our collection, but there are a few. Try searching the library catalog and using the term "cartoon."
Our databases are not the easiest choice for looking for political cartoons. If the web links aren't helping you find what you need, try using Google images. Be sure your cartoon is from an authoritative source though and not from a random blog. Useful editorial cartoons will have been published in newspapers or magazines. If you do find a relevant cartoon on a blog with an author who is not a journalist, be prepared to answer a question about why that particular resource is authoritative and useful.