Many comments here-abouts asking why all the Dems are rallying to Obama's defense these last few weeks. The implication is that individual Dems are choosing to not extend themselves.
"What's X doing for Obama??"
X is doing exactly what X is asked to do. If Hillary hasn't been holding Obama rallies daily it's because the campaign doesn't want her to. If Biden isn't holding his impromptu street-corner press conferences to say McCain is getting stupider by the day, it's because the Obama campaign doesn't want him to. And so on...
The reality is that 99% of Dems would, if asked, go on any TV show in the world or speak at any event to defend Obama. So it is reasonable to conclude that they are not being asked. (These folks generally like giving speeches and being on TV.)
Obama is running a tight ship. It appears that he doesn't want anyone out there except a handful of tightly coached surrogates. Some probable reasons for that include:
1) He ends up having to defend any gaffe made by a Dem defending him, and freelance defenders would cause more problems than they're worth. If he has to defend whatever Ludacris says he would certainly have to defend whatever his own party surrogates say.
2) His position stances involve a lot of implication and subtle deception and amateur surrogates cannot be expected to defend positions they don't really understand. That's not snark, it's political reality. Obama's public stances are not always the same as the traditional Dem package, which is all the average Dem is competent to speak to. If Dems were all over the place on TV discrepancies would accumulate daily... the campaign would become about whether Obama agreed or disagreed with some surrogate's idea of what his position is, or should be. And, again offered without snark, Obama does not know what his positions will be in a month. (Neither does McCain.) The campaign is dynamic. Obama himself can be charmingly vague on positions that are "to be determined," but freelance surrogates cannot be depended on to take no stance, and will get twisted into knots if they do. (The existence of a position paper on a campaign website is not a news-cycle driver. The fact that Obama has a written position on something is not the same as a juicy sound-byte of someone saying something.)
3) He is not really running as a Democrat and having the party rally 'round is not necessarily helpful in his goal of presenting himself as a non-partisan figure. It's a high risk strategy, but it's a strategy. (Since generic Democrats are running ahead of Obama he might want to rethink that. If he gets in trouble in the polls that will change... a partisan Democrat won't get 60% but is guaranteed 51%.)
4) The majority of potential party defenders are in Congress, and Obama does not want to be associated with Congress, aka The Most Despised Institution in America in 2008.
5) He has made a tactical decision to not have anti-McCain sound-bytes. Most hits on McCain are from campaign staff and in written form. Assuming you had concluded that is the right tactic, would you trust freelance surrogates to NOT say anything nasty about McCain?
Love it or hate it it's a conscious strategy, and it is not fair to blame Dems for not taking a role they are being asked not to take.
A thought experiment: If any Dem were asked to go out and slam McCain and refused, wouldn't that be all we heard about from ghouls like Politico? I doubt anyone is refusing.