Swift was the man when it came to political satire. You never quite knew when to take the guy seriously, since he also wrote serious political pamphlets on religious discrimination and England's rule over Ireland. If you look closely at A Modest Proposal, you can see that Swift added in some legitimate suggestions for improving Ireland alongside his satire. He even addresses the agenda of his political enemies, the Whigs. See "In a Nutshell" for more on how Swift's political satire was misinterpreted by the Queen of England. If there was anything Swift was good at, it was getting under people's skin.
In A Modest Proposal, the narrator takes on the role of corrupt politician in order to give us a birds-eye view of hardhearted British public policy.
Swift's Tory politics are evident when he discusses Catholicism in A Modest Proposal.