As the youngest of six, I learned a very important lesson about snowball fights - the key to winning is quantity, not quality. As long as you stay low, scoop fast and throw faster, you'll be the one on top, grinding yellow snow into your sibling's face.
I think Hillary is applying the same strategy to this primary. Plagiarism, matching funds, and the rest - none of these issues are meant to have any real heft. Instead, it is just about associating Obama's name with controversy. Over and over and over again. Relentlessly. None of it is meant to stick, just to get him on repeatedly the defensive and off message. So far, Obama is using just the right strategy to counter this - an unflappable calm that can't be shaken by poorly aimed snowballs. If Obama stays with this strategy, I guarantee he won't be the one who ends the primary with yellow snow in his face.