Pretending that this doesn't hurt the McCain/Palin ticket is denial.
It should not matter, and it's wrong to make her a target or to involve her family in politics this way. But that's the way politics are done here-happens to all sides.
...
The thing is, there isn't a negative here for any flavor of social conservative I'm aware of. As was said, the things they believe in are designed to prevent these situations in general (because they are usually not good in general), but, regardless of smears, the basis is
love, not puritanism.
1) She had premarital sex, but her mom is in favor of a more abstinence-based education. But the girl is 17 and kids do dumb things.
Net loss of conservatives - 0; with a net possible gain from comprehensive sex ed. salt-of-the-earth types whose kids also go against their wishes and teaching and they have to deal with it on a host of issues.
2) She is having the baby when it would be perfectly legal in AK without parental consent, but her mom is pro-life.
Net loss of conservatives - 0; with a net possible gain from pro-choice s-o-t-e types who also have family or friends dealing with teen pregnancy and keeping the baby.
3) She is marrying the father of the baby, and her parents (and presumably his) are supportive of the young couple.
Net loss of conservatives - 0; with a net possible gain from s-o-t-e types whose grandparents, parents, themselves or their kids did the same thing and the relationships worked out.
4) The left can hit her with snarky "See how well your "family values" work, neener neener." attacks, but that won't resonate with many parents or people who sympathize with a less-than-desireable situation for a kid.
I don't see this affecting enough of the base to matter but rather increasing her resonance with normal folks who may differ with her on some issues.
As you say, personality matters and America loves this kind of schmaltz.