Could it be the problem was the “VOTING VIOLATION” mailer?
Was that, too, copied from past “successful” uses?
That, to me, WOULD look like something serious and it is as badly misleading as those flyers that say that you are one of three people, one of which wins the Powerball.
These things are marketed and sold as packages to political campaigns, tested and honed as far as headline, copy, even colors used, all directed at increasing desired response. It’s a product with a history, not a one-off sort of thing that somebody just pulled out of their nether regions. It’s more typically been associated with Democrats, however. I suspect the reaction of recipients has been somewhat different.