I was going to ask if there was any mechanism or precedent for doing something like that, but then I remembered that the Guardians of teh Norms from 3 years ago are now allowed to do anything they want.
No precedent that I know of for that scenario per se. But what’s to stop them? If Kamala resigns Biden is entitled to name a new VP. The new VP has to be confirmed by the Senate however, so if they want Newsom or some other lefty “star” they’ll need to do it before the midterms. McConnel will likely reuse to seat anyone the left would be excited about.
When Spiro Agnew resigned as Nixon’s VP he was replaced by Ford. Granted the purpose of Agnew resigning was because of his own corruption rather than any chicanery on the part of Nixon to get someone else to replace him after resigning himself. Had Agnew not been caught and shown to be a corruptocrat he would have been likely viewed as an ideal replacement for Nixon.
John C Calhoun is the only other VP to resign. He had already lost the election for VP to van Buren (this was before POTUS and VPOTUS ran together) and did so basically to be able to continue to confound Jackson from the Senate.