As a warning for those listening to this week's podcast in the section about Al Gore there were some numbers pulled out of our asses that had no relation to reality. Things about numbers of delegates that Al Gore would have to get to force a second ballot. I apologize, because I hadn't spent much time thinking about it before hand, but the way I was talking about it was of course complete BS. I was just making crap up. I did start to allude to the right answer in the podcast, but never actually articulated it. So I will do so here.
So, OK, here is the deal. And this should actually be obvious, and I was a dumbass when we were recording. It is all about denying whoever is ahead their majority. This could take many delegates, this could take just a few. And "how many are needed" all depends on how close it really is. What is the "Gap" between the candidates.
Assuming Obama is in the lead, to force a second ballot you need:
Clinton + Edwards + Gore > Obama
(and of course Clinton still not getting a majority herself)
Doing a little algebra:
Gore > Obama - Clinton - Edwards
The Obama/Clinton gap right now is 139 delegates. (So Obama-Clinton=139). Edwards has 18.
So if that gap did not change at all, and the Edwards delegates stay Edwards delegates, Gore would have to get more than 121 delegates to force a second ballot.
At this very moment there are 340 superdelgates who have not yet declared a preference. So Al Gore (or whoever) would need to get 36% of these remaining unpledged delegates to make this happen.
Of course, between the remaining primaries and superdelegates changing hands, that number *will* change.
The more Clinton manages to narrow the gap, the fewer people have to go for a third candidate to force a second ballot. If Obama manages to increase the gap, then it becomes harder, and more people would have to go for a third candidate.
It is directly linear with the delegate gap between the candidates. Basically, the number of delegates who vote for "someone else" has to be more than the delegate gap between the two leading candidates.
It is that simple.
(Given all this, I'll reduce the 15% chance of this happening that I mentioned in the podcast down to 2%. I really don't see this happening unless both Obama and Clinton completely self-destruct.)