With the primary approaching in May, soon many residents will find door hangers to mark the visit of a candidate or campaign workers for a candidate. A campaign that has opted for door hangers demonstrates they care enough about their message to want to leave it for you in a less offensive manner than sticking it in your mail box (which is against the law) or leaving it on your porch to blow around and decorate the neighborhood with.
When I'm asked by candidates whether they should opt for print outs, which the smaller ones are called "palm cards" or door hangers, I say both. Palm cards for the voters who are at home when you call, door hangers for the ones who are not. Nothing turns off a prospective voter than coming home and finding a bunch of campaign material in their yard, it's well worth the small extra expense.