UPDATE 5:00am: It looks like Howie might have found the culprit within the Ted Cruz campaign. A guy named Christopher Larimer works for Ted Cruz, and previously put a stunt like this together in Alaska. As outlined in a 2014 PBS article:
http://www.pbs.org/newshour/rundown/will-shame-drive-alaskan-voters-polls/
It included the addresseeâs voting history as well as those of their neighbors, and contained something of a threat by promising a follow-up letter to show the results of the upcoming election. Larimer says they got complaints, but the technique worked quite well. (read more)
Good catch!