Per linked article: Since their campaign account was registered with the Federal Election Commission in the name of both candidates, Harris could use those funds for her own presidential effort if Biden were to drop out, according to Kenneth Gross, senior political law counsel at Akin Gump and former associate general counsel for the Federal Election Commission.
If the reverse were the case, Biden took the Vice-Presidential nominee position it should follow that any candidate, including but not limited to Harris could be the Presidential nominee.

Who Could Replace Joe Biden?
(Image by ANNA MONEYMAKER/JUSTIN SULLIVAN/KEVIN MAZUR/JEAN CATUFFE/GC) Details DMCA
With the possibility of post-general election turmoil, a Democratic ticket with Biden as Vice-Presidential nominee, would have the apparel of the Most-seamless transition!
In addition, Biden as Vice-Presidential, would provide the U.S. with an administration with the strongest Vice-Presidential in our history.




