Challenge: Make the convention deadlocked between Clinton, Obama and Edwards. Bonus points if they nominate someone other than the above; more points if he/she wins in November.
The key prerequisite for this is to have Clinton hire someone who actually knows how the nominating process works and has enough clout inside the campaign to force a change in strategy such that the large bloc of February caucus states weren't effectively abandoned to Obama.
With Edwards, you need to conjure up some scenario where he stays in the race through Super Tuesday and breaks threshold in enough places to pick up a chunk of delegates. There is no way that he remains viable as a candidate through the convention, though. His own staffers were plotting to leak the story of his affair if it looked as though he could be the nominee. One possibility is for Edwards to win, by the narrowest of margins, Iowa. Obama, being very well-financed, stays in the race and wins South Carolina and Nevada while Clinton wins New Hampshire. That should keep all 3 in the race until the Super Tuesday contests in February. Post-Super Tuesday, Edwards staffers worried that he might win the nomination leak the story of his affair to the media and he drops out. Clinton and Obama then battle state by state for delegates and, in a contest where nobody develops a big lead in delegates, the Edwards delegates and superdelegates wait it out and, for the most part, remain uncommitted. In this scenario, the battle over the disputed delegations from Michigan and Florida because of their early primaries has enormous stakes and a very uncertain outcome. The solution that was devised -- seating the delegates, was made when the nomination was effectively settled. It's quite possible that in a scenario where seating them would favor one candidate over the other, the DNC Rules Committee might stick to its guns and punt the issue to the convention's Credentials Committee, which in turn would be a major battle in its own right and, in all likelihood, a very messy one.
I don't think Obama can win SC if he loses IA.
FRom my understanding, what sold South Carolina on Obama was that Iowa showed that whites were willing to vote for Obama making him a serious candidate. Here, you're asking him to win Nevada after losing Iowa, and that propelling him to victory in South Carolina with a reinvigorated John Edwards still in the race who has already (implausibly after winning Iowa) lost Nevada. There are two things which set Iowa apart from Nevada, and both work against Obama in South Carolina. Nevada is more diverse demographically, but especially racially, and the workers there are rather more unionized than in Iowa. The unionization ought to help Edwards, but if it does not, and Obama wins Nevada, it remains less evident that whites will clamour for Obama, and Edwards has roots in South Carolina, a fact which would likely boost his vote share there.It is conceivable if you have a 3-way race and a razor-thin loss in Iowa. The black vote in SC is huge and had started to swing to Obama before Iowa. I also gave Obama a win in Nevada, which was a week before SC. One thing to remember is that Obama was extremely well-financed; the money was there to compete effectively in SC. Another factor in favor of Obama staying in the race is that the rumors about Edwards were floating around all the campaigns; you don't end a campaign if you think one of the candidates may implode.
Getting Edwards a win in Iowa isn't actually all that far-fetched. In May 2007, a memo leaked from Clinton's deputy campaign manager raising the idea of not competing hard in Iowa. The backlash from the leak caused Clinton to double-down in Iowa, but the rationale for passing on Iowa was actually not that unsound. A suitable POD, then, is that the memo is never written, or never leaks, and Clinton decides to spend more on New Hampshire and the early caucus states rather than squander some $30 million in Iowa on what was fairly unfriendly turf and Edwards manages to pick up enough of the Clinton supporters to eke out a narrow win.