[pgkdan]

Q: If a pope is a heretic, does his successor still have a valid claim to apostolic succession?

As far as I'm concerned there is no such thing as 'valid' apostolic succession.

[Romulus]

So the apostles had no successors?

[Gil4]

As far as I'm concerned there is no such thing as 'valid' apostolic succession.

Sorry, I mistook you for a disgruntled Catholic. I agree, but I wanted a Catholic take on how that works. (There has been at least one pope declared to be a heretic by his successor, so I'm still curious.)