The fringe far left, who believed Bush was going to start a war in Iran and declare martial law to cancel the 2008 election? I wish ToxicAdam was here, he certainly remembers those threads.
Fahrenheit 911 also made the general argument that Bush was an idiot but also well connected to a variety of complex conspiraciess. I spent a lot of time listening to Randy Rhodes during Bush's terms, and posting on her forum; in terms of paranoia there isn't a large difference between the fringes of either party. The ultimate difference comes from how the mainstream of their political parties accepts them. Republicans feed the frenzy. Democrats gave them some winks with respect to Iraq war conspiracies (pipelines), but overall they shunned the nonsense. Remember how democrats embraced Cindy Sheehan before she went off the deep end? Republicans make no distinction, and prop up conservative versions of her nonstop (Benghazi, Obama personally sending an imam to damn Navy Seals to hell at their funeral, F&F, etc etc).