Here we go she resigns, Biden picks Hillary to replace him. She declares 25th on him.
Scary scenario but could happen.
This is the scenario I'd like to see, no matter how improbable: After the November 2022 elections, Republicans win both the House and Senate. Both Biden and Harris are impeached and the Senate, with Dems fed up with both, vote to convict making House leader and Speaker McCarthy president. Otherwise we continue with Dems in charge of the Executive Branch until 2025.