I agree with Ross that Colin Powell would make a formidable third-party candidate. One of the political peculiarities of the Iraq War was the habit of Democrats to increasingly associate themselves with Powell's views, particularly as expressed in the Bob Woodward books (remember the "Crate and Barrel" theory of Iraq?). Even as Powell used his awesome credibility to enable and accelerate the rush to war, esteem for his person remained oddly high, as Powell was cleaved into two separate beings: The "real" Powell, who was cautious and realist and wise; and the "soldier" Powell, who fell in behind George W. Bush because, well, that's what a good soldier does.
It's never been quite clear to me how you could separate the two, but in their rush to wrap their criticisms of the Iraq War in Powell's credibility, many Democrats ended up preserving the legacy of a man who was, aside from Bush and Cheney, arguably the most instrumental figure in pushing the country to war. It's hard to imagine Powell mounting a campaign for 2008, but were he so inclined -- and it could well have happened -- the Democrats' reliance on him would've proven troublesome indeed.
