John Edwards has stated he is in this race until the convention, and I believe him. I don't think that either Sen. Obama, or Sen. Clinton would ask him to be the VP candidate, and I don't know how interested he would be in having that job, anyhow.
On the other hand, Senator Clinton has said that she is only in the race for sure until Super Tuesday. Let's consider the following: right now, HRC and JRE have the same number of delgates, and BHO has only one more. Even with a double digit victory over HRC, the number of delegates that BHO picks up proportionally isn't enough to give him 50+1% at the convention -- and then there are the Superdelegates to consider -- which hold about a quarter of the votes.
Would HRC dropping out give JRE a real shot? What about a brokered convention? Because even winning all the primaries, with the kinds of margins we are seeing now, puts us into a whole new ballgame on the second round of balloting ...