Someone has to keep the postal carriers employed and the paper-recycling machines humming. And these, near as I can tell, are the main uses of campaign mailers.
At our house, each day's mail is first sorted into two piles. One has the envelopes I'll actually open, the periodicals I'll actually read. The other, usually much larger, is the junk mail: The advertising vehicles masquerading as magazines. The never-ending charitable appeals from nonprofits I already donated to for the year, which always makes me feel as though my donation has simply been spent on more fundraising. And at this time of year, the stuff that goes first into the junk pile are the campaign mailers.
Why would I pay any attention to them? Decades ago, they ceased to give me any real information. There are the slate mailers that were paid for by the candidates and thus don't reflect any real endorsements. There are the misleading attacks on each other that the accused has little or no chance to respond to before election day. They hint that the candidate has endorsements that he or she doesn't really have. (See this post on Sheila Kuehl by my colleague Kerry Cavanaugh.)
An acquaintance of mine, who's working for one of the major campaigns, was fretting the other day because an opponent had sent out an inaccurate smear letter to voters. The campaign was wondering how best to respond. My response was, "Is anybody going to actually look at it?" Why would a voter trust an ad from a particular campaign as a source for making a ballot decision? With all the readily available information about elections, this is like giving serious consideration to a mailer from a tobacco company that says how much it cares about the public's health.
Direct mail is a big part of the campaign scene; one would think there are some data to show that they do something. I have to wonder. I give the mailers just enough of a glance to ascertain what they are, not even from whom, much less what they said. Then into the recycle bin they go.