The What Now?

Every so often I skim through the comments that Blogger tags as spam just to see if there's anything legitimate in there.
There never is, but I do invariably find myself puzzled by what is in there.
Sure, there's the standard links to Web pages featuring sexy girls and for cheap prescriptions and whatnot, but there's a lot of random comments about US politics.
One of the more common ones - the same four or five comments keep appearing and reappearing verbatim - is some airy nonsense about the transformative effect of the Tea Party, but by far the most puzzling one is the comment referring to John McCain - McLame, as the comment spam puts it - being a "Manchurian Candidate."
Given how rarely I mention politics here, it goes without saying that the comments are apropos of nothing contained within the posts to which they're attached, and the comments don't actually contain any links, so I'm just puzzled as to why they exist.
Clearly it's the work of some sort of spambots, but what, exactly, are the comments themselves intended to accomplish, given that they contain no links?  Just some sort of random comment thread crawler that posts a comment in the hopes that it will receive a response, at which point it will then spam it further, this time with actual links?  Is it a bot set up by some comment troll who's feeling around for some thread in which he - of course it would be a he - can get people riled up with some sort of inflammatory rhetoric?
I just don't get it.