I don't think very many pro-lifers expect him to mention abortion at every campaign stop (at least I wouldn't if I lived in California.) But simply saying that its "set in stone" at the state and federal level isn't good enough.
To reframe the debate and get away from stereotypical 'pro-life'/'pro-choice' hot buttons; the life choice advocates gain much in defeating the liberal argument by assuming the 'life' side of the 'choice' discussion. The other 'choice' is not pretty, nor easy to side with, unless you are a beneficiary of the 'federal funding' that accompanies 'Planned Parenthood' and the 'choice' programs it currently endorses.