It could be because Obama just naturally sparks more enthusiam in people who are strongly interested in partisan politics than Hillary Clinton does... ;-)

After all, what does "rabid" mean in the political context? It means strongly partisan. Is that bad or is it good? Depends on your given set of prejudices, I guess.

I don't belong to any political party, and never shall, by the way. So I'm a bit wary of people who are overly partisan.