Does a change of counsel affect the merits of a second habeas corpus petition?

Petitioner concedes that whether there has been a change of counsel is irrelevant to whether the merits of claims raised for the first time in a successive petition should be entertained. The rule has been that the court will look to what petitioner and/or his counsel knew at the time of the appeal or the filing of the first habeas corpus petition, and demand that the failure to raise all issues in a single, timely petition be justified. Any other rule would put a premium on repeated changes of counsel, and would wholly undermine the policy underlying the court's refusal to consider the merits of successive petitions offering piecemeal presentation of claims. And, as we have indicated above, in the future a habeas corpus petitioner, like a petitioner who mounts a collateral attack by petition for writ of coram nobis, " 'must show that the facts upon which he relies were not known to him and could not in the exercise of due diligence have been discovered by him at any time substantially earlier than the time of his motion for the writ.' " ( People v. Shipman, supra, 62 Cal.2d 226, 230, 42 Cal.Rptr. 1, 397 P.2d 993.)