Why are "grass roots" so important to the success of a party's candidate?

Read the following: (1) liz has become more responsive to her partner's advances since a really beautiful woman moved in next door; (2) unable to accept his desire for other young men, 15-year-old juan immerses himself into his studies; (3) shauntel tells people that her coworker mary dislikes her; though if she were honest, shauntel would realize that it is actually she who dislikes mary; (4) "ben's nasty; he's disgusting," says renee; but renee secretly finds ben attractive. describe the defense mechanism he or she is using.