Less than half of eligible voters actually vote. Common wisdom is that the majority of Americans are just too lazy and apathetic to be bothered, I don't buy it.
I think most of those people just don't believe it makes any difference, that they'll be screwed either way.
If a third party could get half of those people to the polls they'd win in a landslide even if every current voter stuck with the mainstream parties.
Someday soon a third party candidate is going to be viable, probably not in '08, but soon enough that we need to be considering it. The current economic/political status quo is unraveling, and the real implosion is yet to come.
When you vote for evil, even if it's only to keep the greater evil out of power, you empower that evil, it grows, soon it's just like the greater evil, and the greater evil is even worse. That's assuming of course that the system isn't designed to do just that, making them all equally evil, since they're all playing for the same collectivist team...
I said in '04 whatever party was in power after the 2004 elections was likely to fall apart before 2008, they've actually done a better job of spinning things than I thought possible, but 2008 is a long ways away yet, I don't think this will be the arguement in 2008, it'll be what the hell are we going to do about the mess we're in?