Can Biden be replaced as Democrat nominee? Who could replace him?

The first presidential debate is done and the aftermath has not been good for the incumbent, Joe Biden.

Some Democrat politicians and operatives reportedly texted CNN commentators with hopes that Mr Biden, 81, would step aside. Some floated the possibility of going to the White House and publicly stating concerns about him remaining as candidate.

But if Mr Biden were to drop out, it would be a free-for-all. There is no official mechanism for him or anyone else in the party to choose his successor, meaning Democrats would be left with an open (Democratic National Convention (DNC) in Chicago from August 19-22.