Apart from Al Gore, the most prized Democratic endorsement still out there belongs to the senior senator from Massachusetts. Both the Obama and Clinton camps have been working Kennedy hard. But I'm told not to expect him to pick a side before February 5.
(My off-the-cuff hunch, incidentally, is that that's a letdown for Hillary Clinton. Kennedy is a real creature of Washington who worked well with the Clinton White House and has backed establishment candidates--Al Gore, John Kerry--in past primary fights. I would think his default choice would be Hillary. On the other hand, maybe he finds those RFK comparisons stirring...)