Quick thoughts on Nader
Now that he has thrown his hat into the ring for the 2008 cycle, many are predicting that he will again not gain sufficient support and won't influence the general election, much like 2004. I have a different theory, that his running will more closely resemble 2000 than 2004.
In 2000, George W. Bush was not the divisive figure that he was in 2004. "Bush Derangement Syndrome" was an unknown term. Whether it was Bush or Gore, 2.74% were ambivalent and decided to cast their vote for Nader to make a statement. By 2004 the hatred for Bush took over, and people may have considered Kerry the lesser of two evils--they may not have liked him, but they hated Bush. I think Independents were more prone to vote for a third party in 2000.
Now, here we are in 2008. The Democratic party is doing whatever it can to disenfranchise it's electorate. As much as Howard Dean likes to say that McCain will just be a third Bush term, most Americans recognize that this is just Rhetoric. Thus, I don't think Bush hatred will keep people away from McCain. In short, we are in a situation more similar to 2000 than 2004, and I think Nader could receive a few percentage points in the popular vote...perhaps enough to determine the outcome again.