Can an individual sign a petition, and fill out a voters registration card on the same day?

[antiquie]

4. Depends on your state.

California Petition Signatures

Only persons who are registered, qualified voters at the time of signing are entitled to sign the petition. A person can only sign a petition that is being circulated in his or her county of registration. If a petition circulator is a registered voter, he or she may sign the petition he or she is circulating. (Elections Code §§ 105, 9020, 9021.) Each signer must personally place on the petition his or her signature, printed name, residence address (or physical description of the location if there is no street address), and the name of the incorporated city or unincorporated community. (Elections Code § 100.) None of the above may be preprinted on the petition. Each signer may sign an initiative petition only once. (Elections Code § 18612.)

I'm not certain, but I don't think the voter is "qualified" until the registration is accepted by the SOS.