I was going to point out that when the Whigs died out, there had been a tradition of strong regional parties (Anti-Masons, Anti-Federalists, etc), which made the collapse of a major party less shocking-- folks had something to jump to, as compared to the almost nothing they'd have today. (Natural Law Party? Bueller?)
    But then I started thinking about how third or smaller parties seemed to have done better when communications was a lot slower, and a lot more dangerous the further west you went. Were third parties doomed to obscurity the day the telegraph (or as one author has called it, "the Victorian Internet") shortened communication delays from days to minutes? On the one hand, there were fairly national groups like the Know-Nothings, who IIRC elected candidates on both coasts; OTOH, it is true that there have only been two significant third party runs since the telegraph (Theodore Roosevelt, and Perot) became widespread. Something to meditate on while I'm stocking books tomorrow.

     As far as the current day goes, a party collapsing today would be catastrophic, and probably a sign that civil war was coming up quick. But I can't think of anything big enough to actually demolish or split one of the two major parties today. Conservatives made some noise about trying to eliminate the Democrats during the last couple years, but this was due to something along the lines of mass hysteria, and some kind of masturbatory political fantasy. (Which describes a lot of conservative bestsellers, actually.) If, as I believe, winning elections means cobbling together enough single issue voters to put a candidate over the top, then any party based on this strategy is going to be awfully difficult to tear apart from within-- and impossible to remove from without. Of course, every status quo looks stable until it falls apart . . .

    Thanks for reminding me-- next time I see a copy of The South Was Right come through the store, I should buy it.

Ex ignorantia ad sapientiam; e luce ad tenebras

The Whig party's problem was emblematic of the nation's problems. It was built of an anti-Jackson coalition so it included both "States Rights" (ie pro-slavery) Southerners and protectionist northerners who were anti-expansion and thus anti-slavery. Slavery is absolutely what killed the Whigs. It's not too different from the unholy marriage of the Religious Right and the George F. Will wing of conservatism. The only question is will an issue rise up with such force as to drive a stake between the two. Should the economy continue to falter and the Clintonian internationalist interests push further North American unification, that would be the only issue I could see splitting that party.

It is easy to buy small plaster models of what you think life is like.

     Yeah, the lesson would be then that a little power only increases the thirst to have more. It could also just mean that these third parties are the source of change for the larger parties, because when they hit a certain level of popularity (think Ross Perot), the two large parties quietly change to reflect the changing times. To put it in lofty terms, they're the churning that keeps stability from descending into stagnation.
    OTOH, it could just be that the populace drives the politics, which would mean that Americans just aren't that interested in change, and are fairly homogeneous when you get right down to it. (Ezra Pound suggested as much in the 30s, IIRC the date correctly.) Which would make third parties the outlet for those kvetching without intending to enact real change-- a constant whining in the face of good times, to be uncharitable.
    Nah, probably not, as appealing as that is for me; the activists appear to believe what they say, and it would be very bad faith (on my part) to question their sincerity.

Ex ignorantia ad sapientiam; e luce ad tenebras

Which is the point of profwhat's post, I think.  Politics is the art of the possible -- it's what results from negotiation and compromise.  The problem with many of the third parties is it's all or nothing at all and members find themselves comfortable with that position.  Nothing wrong with that if you're psychologically prepared to forever be on the fringes of political power in the US.  I've flirted with third parties and voted for enough third party and even non-party candidates (I wrote in McCain's name back in 2000) in my day.  But, I've become enough of a realist and fatalist to realize the two party dynamic which typifies politics US-style is simply never going to change, at least not in my lifetime.

Illegitimi non carborundum.