"Of the people who appear to have their hats in the ring so far, I only see Walker and Cruz as electable."
I agree with your assessment that any candidate must be acceptable to SoCons to get the nomination or have a chance of being elected in the general.
SoCons must perceive their candidate is God-fearing, goes to church, is opposed to Abortion and Gay Marriage and always has been.
On those they will not compromise.
Unfortunatly, that lets some pretty weak candidates into the tent:
Bush, Rubio, Huckabee, Santorum et al.
Sure, some of their positions slice with thin nuance, but their positions on the core social issues are, by and large, in conformance with SoCon principles.
And, ostensibly, acceptable.
I don’t see any of the open borders crowd flying at all with social conservatives as a whole. Huckabee can slide by the illiterates who have never examined his records.
Keeping rapists and drug dealers out is and quintessential social issue.