Can Davis himself run as a candidate to replace himself? ISTM that if he can, there is almost no way he can be ousted from office, assuming - as is very likely - that more than one Republican and no other Democrats run. But I have not seen this option discussed.
Unless the problem is that all his supporters will vote against the recall instead of voting for him as a replacement candidate. But that brings up another question: does a person who votes against the recall get to vote on a replacement in case the recall goes through? If yes, this objection is moot.
Gray Davis CANNOT run to replace himself. He is one of the few people who is ineligible.
Of people over 18 who live in California and are registered voters, I think the only others who might be ineligible are Gerry Brown, George Deukmejian, and Pete Wilson because they all would have term limit issues.
You are presupposing that a successful recall of Davis is likely. That is a big assumption. The most recent polls showed that the public was 51-43 in favor. That’s not a huge margin to overcome.
As for the replacement election (if Lieutenant Governor Bustamante decides that there will actually be one, that question is still up in the air), everybody can vote in it. Just because you vote “No” on the recall, doesn’t mean you forfeit your selection to vote in the other election.
I don’t know if voting equipment would be sophisticated enough to determine that someone voted “No” and then have the rest of the ballot not count.