Below are some recent stories/reports about political spamming:
Also, here are two law review articles from 2002 (I think) and 2004:
I have a few comments.
Currently, I am not purchasing any email address lists.
It is my understanding that Google has spam limiting systems in gmail (which is the email I use). For example, it is my understanding that Google limits a user's sending of emails to about 500 emails a day, which number can be affected by such things as the number of delivery failures or the number of newly acquired email addresses that are utilized. If the limit is exceeded, Google disables the gmail account from sending emails for 24 hours.
There is a possible silver lining in political spamming. To the extent voters are angered by the amount of political spam that gets into their email inboxes, voters may be sufficiently riled to say to themselves and their friends, "Who are these jerks who are spamming me/us? I am going to find out about them to see if there are any who are not jerks, vote for ones who are not jerks, and tell the others they are jerks and I am never going to vote for them."