This seems sensible to me. Obama hasn't really gone after Clinton on this sort of stuff--the Kazakh guy, the tax returns, and so on--and he is the frontrunner at this point, so it doesn't make much sense for him to do so. Some might say that Obama's not playing on this level is a point against him, and that he's not willing to do what it takes to win, but I'm not sure. Obama doesn't seem to be willing to play especially dirty because he probably doesn't want to see the eventual nominee dirtied up because of him. It could be because he's a team player and realizes that he would have to work with a President Hillary Clinton if she were elected, and maybe it's because he's got decades to get elected president and he figures that if it doesn't happen this year, he doesn't want to poison the well for later. Perhaps it's because he doesn't want to alienate the Clinton-loving Democrats in the primary and general elections. Or maybe he just believes that maintaining the progressive coalition is more important than him getting the nomination. In any event, it doesn't necessarily mean he'd refrain from being the first to throw an elbow at John McCain (which he has been doing as of late).
Contrast this with the Clinton campaign, which has tried to inject racial politics into the primary campaign, which has attacked Obama on issues where he and Clinton actually agree, and has made noises about wooing pledged delegates away from Obama that were later disavowed. Granted, it hasn't been that nasty, but I've gotten far less of a sense from the Clinton campaign that she's much of a team player. If she loses, I don't doubt that she'll make an effort to actually see Obama elected, but her attitude seems to be more along the lines of "I'm going to win any way I can, even if that means exploiting every loophole I can find," instead of "I'm going to make my pitch and let the people decide." I'd just like to see Clinton say something along the lines of the second message every now and then is all.
