The good news is that, for this group and for political organizations, Blacklists work great. You block their addresses, and they don't bother you any more.
This is my personal Blacklist as of today. Canon is the newest addition. To get on here a legitimate company or political organization has to keep sending me spam despite my clicking a remove-me link. If a persistently spamming corporation doesn't have a one click remove-me solution they go right to the list.
antec.comI'll update this post as I add more brick and mortar corporations with serious spam problems. Of this list I was most impressed with Gourmet.com -- they were relentless spammers. SONY media was almost as bad -- heck, come to think of it, they were all really bad. Canon went to the Dark Side about two months ago.
theclubbingforum.net (no, I have never been a customer)