Barack Obama.
The rough outline of his argument is this: The 22nd Amendment doesn’t say you can’t be president for more than two terms. It says you can’t be elected president twice. If a Biden-Obama ticket won (which we’ll get to), and tragedy were to befall Joe Biden, Barack Obama could become president, according to the letter of the law (which we’ll also get to), since he wasn’t elected to the position. As such, Obama is not constitutionally ineligible to serve as president.
Ergo, Harris could pick Barack Obama and have him confirmed through a House and Senate vote, which at this unique time with a 50-50 split Harris casts the deciding vote.
Honk-Honk!
May as well since he is calling the shots already.