Hillary Clinton won’t withdraw unless she has to. But anxious Democrats will be so worried if she fails to be able to campaign and her health escalates as an issue that they might bring unbearable pressure on her to step aside. If that happened, the Party rules state that the Democratic National Committee — two from each state — would be empowered to nominate Joe Biden.
http://www.dickmorris.com/hillarys-health-dems-replace-biden/