Pros
Fun, social, group-oriented company. Casual. No experience necessary. Good physical exercise. Get to do something you care about.
Cons
Minimum wage only to walk for hours in the heat or cold, knocking on strangers doors, many of whom do not answer or tell you to go away through the door/intercom, when you do finally get someone who agrees with you they usually are a tight-fisted rich person who is terrified to part with twenty dollars, and often encounter good-hearted poor people, senior citizens or college students who will sign petitions but wish they could donate and can't give you more than literally five dollars. Once in a while someone will yell at you. If canvassing in Los Angeles you will start to hate hypocritical rich liberals with a fire that might make you join an anarchist organization as a result.