Hillary’s running mate would then become the donkey’s nominee.
I don’t think so.
Anyone selected as Hillary’s running mate will be some far left loon. Selected to shore up the socialist/minority/felon/illegal alien wing of the party but completely unelectable outside of that wing of the party.
I understand the parties have rules to cover such instances, but I do not remember the Democrat having any qualms about changes rules to fit their ends.
Of course, I fully expect Hillary to be the nominee and Comey to retire a very wealthy man.
Both parties have rules that empower the standing national committee to name by majority vote a replacement presidential candidate, and neither party requires that it be the vice-presidential candidate.
Vacancies would be likely be filled by the national committee up until the Electoral College vote, although there are some murky details.