To state the negative, social conservatives are powerful enough to cause any liberal Republican to lose.
What they are not is powerful enough to ELECT one of their own to statewide or national office. The only way a socon-sympathizing Republican can win a general election is if RINOs and independents think that he doesn't really mean it.
That's why the prospect of a Santorum nomination is so bad. The socons may be powerful enough to nominate him, but they are far, far away from being able to elect him.