The NYT finally solves a puzzle for me by explaining the basis of fundraising collaboration between the Clinton camp and the Obama camp. Clinton has more than enough money in the bank to pay her campaign debt (more than half of which is to herself). But she can’t use it for that purpose, because it’s general-election money from donors who maxed out their primary-season contributions. As I understand it, she can either give the money back or roll it over into her Senate-campaign warchest.
So if Obama mobilizes some of his maxed-out donors (he’s already got $10 million in “general election” money, which means those donors are over the primary-season limit) to help out Clinton, and she mobilizes some of hers to help Obama and the DNC, everybody’s happy.