How does Miller contrast Abigail and Elizabeth in The Crucible and what is the dramatic impact on the play?

Abigail and Elizabeth are polar opposites on the characterization scale. Abigail is highly emotional, while Elizabeth is colder and more restrained. Abigail accuses Elizabeth of being a chilly, sour woman, but when she finally appears onstage, the audience can see that Elizabeth is chilly mostly because of her husband's infidelity with Abigail. Interestingly, both characters can be very vindictive: Abigail gets vengeance for her disgrace by accusing her enemies of witchcraft, while Elizabeth is cold towards her husband, furious at him for cheating on and humiliating her.
The dramatic impact this creates is to make these two women foils. They are united as foils both in their contrary natures as well as in their relationships with John. Abigail is cruel and unforgiving, and this highlights Elizabeth's willingness to finally forgive her husband. Both represent the duality of human nature: the dark, animalistic side which craves power at any cost (Abigail) and the side which can transcend hurt and forgive (Elizabeth).