Clinton's debt

I really don't understand this idea that Obama has some sort of obligation to Hillary Clinton to help her pay her debt from the primary campaign. Attitudes like this are completely mystifying to me:

Some Clinton supporters are grousing that Mr. Obama has yet to make the symbolic gesture of writing a check for $2,300, the maximum allowable campaign donation, to help retire her debt of over $12 million.

Am I missing something here? Clinton went into debt because she made the calculated decision to borrow money to win the primary. Why should someone else pay it off, let alone the very rival she borrowed the money to defeat? Moreover: aren't the Clintons supposed to be worth far more than $12 million? When their tax returns were released a few months ago, it was revealed that they had earned no less than "$109 million in the the last eight years". So it seems to me that Clinton ought to be more than capable of paying off her debts by herself.