Well, we have a new one. http://freethoughtblogs.com/dispatches/2012/08/06/tn-legislator-sends-out-crazy-conspiracy-theory/ Crazy theory that Obama is going to become a dictator somehow. Now I hate that he has continued and expanded the Bush era erosion of civil rights, but that has been trending among presidents since before Reagan. As a nation grows, centralized powers grows more attached to stability. As such they do anything and everything to maintain the status quo.
This particular "theory" is another false flag accusation, where the evil government will fake an external attack to further centralize power. While the nation actually has done this, or attempted to do this in the past, it has been easier, historically to just use real crises like 9/11 or Pearl Harbor or whatever else. Politics is all about manipulation of the masses to gain more power. Aside from the fact that most of Homeland Security was Bush appointed and has deep ties to Republicans, most of the government would not be willing to play such an obvious hand. If it failed, the entire legitimacy would be shattered, making more subtle power grabs harder to hide.
The Republicans have been using the less entrenched members, often tea baggers, to spout these crazy stores for decades, but the frequency has increased drastically since 2010 and the formation of the astroturf tea parties. Crazy racial theories, accusations of socialism, fascism or whatever other ism they can think of, all used to radicalize the base and scare people into voting against Obama. The GOP has no good candidates, so they hope to demonize Obama enough that people, especially moderates, vote for a GOP president out of spite for Obama.
The worst part is that moderates eat these stories like hot cakes. Or something you eat fast. Self declared moderates are actually conservative, enjoying the status quo almost as much as the powerful people it supports. Moderates decide based on fear, more than any other emotion, and the side that scares them the best wins, even if that party was the one who caused the problem. Current Romney ads focus on some imaginary Obama threat to businesses and white people, because the GOP needs to foster as much fear as possible to make moderates forget that they and the policies they propose caused the recession to begin with. By lying about time lines, misquoting, and unofficially spreading conspiracy theories the GOP is demonizing Obama in any way they can. As long as Romney avoids talking about actual policy, this could work. The more personality he shows, the worse it is for him since the policies and detached attitudes are what people associate, correctly, with the recession. Fear controls the masses.