David Brooks asks:
Why does she go on like this? Does Clinton privately believe that Obama is so incompetent that only she can deliver the policies they both support? Is she simply selfish, and willing to put her party through agony for the sake of her slender chance? Are leading Democrats so narcissistic that they would create bitter stagnation even if they were granted one-party rule?
I think it's quite possible that Hillary simply doesn't think Obama is electable. (See Bill and "all that other stuff.") Now that may be a delusion. But if you believed it to be true, you would soldier ahead. She also does have quite a lot of passionate supporters cheering her on, and is roughly tied with Obama in national polls; that's not easy to ignore.