Larry David, cuz Bernie will be feeling the nurses’ bums by 2020 but Larry should be good for it, he was perfect as Bernie on SNL.
But probably Michelle Obama is being groomed for this honor of being the second Mondale.
Other possibilities, Snowflake-in-Chief Stephen Colbert, Michael Moore himself, the current governors of any west coast states, Chelsea Clinton, and (if he gets fed up with Paul Ryan) Donald Trump.