When I have searched for info on myself it is not easy to find
Haha, man you're crazy I'm telling you
Do you really believe that someone would google your name in order to find your address?
OK, your address is not publicly listed, but most likely it is privately listed - somewhere some entity has a database which contains your name, address and everything (the same of many other people). So most likely someone got an access to this database - hacked it, or payed money for it.
"Why would someone do it?" you would ask, I assume. In fact this is an old marketing trick <yawn>. I would ask you in response: "What would you do if the postcard was typewritten instead of handwritten and it didn't contain you name?" I don't know you, but I can predict with a big accuracy what you would do: you would kick it to the curb and ten minutes after you wouldn't even remember about the post card.
But now you are impressed, aren't you? They caught your attention. It makes a big difference you have to admit.
There is a little "side effect" to this approach - the recipient might get a bit scared. But who cares? Nobody gives a damn about your feelings. Fear might even "help" you to chose the "right" candidate.
And ah- one more thing. You said you live in Ohio didn't you? Check this out then:http://en.wikipedia.org/wiki/Statewide_opinion_polling_for_the_United_States_presidential_election,_2012
The pre-election situation in your state seems to be pretty tied, which explains the aggressive marketing approach. Obviously, the organization that sent you the postcard is strongly dependent on the outcome of the presidential elections.