In comments, people have been discussing the rumor that Sarah Palin's fifth child isn't actually hers, but her teenage daughter Bristol's. Here's a gossip site pushing the story. Evidence: Sarah doesn't look pregnant at almost 7 months, Bristol looks pregnant in some pictures, Bristol dropped out of school for 4-5 months supposedly with mono, Sarah supposedly gave a 30-minute speech in Texas after her water broke and then flew back to Alaska and drove back to her hometown. I wouldn't make an even-money bet on the rumor being true, but after conversations with moms about pregnancy, the rumor doesn't seem wildly implausible to me.
Possible but unlikely scenarios can be worth advising for, so let me say something on how to approach the issue if it turns out that that Trig Palin is actually Sarah's granddaughter. Direct personal attacks on Sarah Palin seem misguided -- the core of what she did actually looks quite sympathetic. She dealt with the pregnancy in a way that minimized the costs to her daughter, which is admirable. She may have had to make a false legal claim of maternity, but that seems kind of nitpicky next to the major human drama here.
The big point for lefty commentators, however, is that these are the wages of extreme social conservatism. If you're an extreme social conservative who insists on abstinence-based sex education, your daughters just end up pregnant from sex without condoms or birth control pills.
Electorally useful (and true) presupposition that this point hammers home: Palin is an extreme social conservative.
Terrifying scenario that this point brings up: If Sarah Palin designs your daughter's sex education, you may have the opportunity to heroically fake being the parent of your Down's-afflicted illegitimate grandson.