Who is the protagonist/antagonist in the Scarlet Letter?

Obviously Hester would be seen as the protagonist, but what makes her so? and who then is the "hero" of the story (Arthur Dimmesdale?).. and although Chillingworth seems like the obvious choice for an antagonist, could it be that it is someone else (as he does not cause the most trouble for the characters)? please offer youre opinions and ideas. any help is appreciated :D