Edwards recently announced that if either of the two democratic candidates were to offer him a vice president position, he would not accept the offer. He has not given any specific reason why he would not accept the job, instead just answering reporters with, "No."
He has also stayed quiet in the past weeks on which candidate he would endorse. However, he has praised both candidates, and at this point it is safe to say that both the candidates will continue to try and persuade Edwards to endorse them. But if Edwards were to endorse one of the candidates, why would he be waiting so long? It is quite possible that at this point he may choose not to endorse either Clinton or Obama.