Reforms initiated by John McCain (credit where due) address some of the problems of candidates loaning money. Other campaigns can help fundraise but can't simply pay off the debts. Debts can be repaid in full before the election, but "only" $250,000 can be repaid to candidates after the election.
The candidate loan problem remains, however, in the period between when the election is actually decided, like it is now for the Democratic nomination to be held in late August, and when the election actually occurs. Winning candidates will get deluged with money from contributors trying to curry favor by putting money in the candidates' pocket through paying off the loans candidates made to their campaigns. Losing candidates who are still powerful, like the Senator from New York, will be even more grateful to people who pay them off.
And while other candidates can no longer bribe a competitor to drop out by paying the loan the candidate made to herself, the fundraising help is significant. Finally, there remains the $250,000 contribution that can happen anytime. Candidate loans to themselves should be abolished.
I also wanted point out a neat trick in money-shifting from Bloomberg:
Unlike the rules for her personal loan, Clinton can tap her Senate campaign account to pay off the vendor debts. While the account had $277,480 as of March 31, she could ask the donors who gave her $23 million for the general election if they would be willing to re-designate that money for her 2012 Senate re-election campaign. That would give her more than enough cash to repay everyone but herself.
People gave to the general election fund because they maxed out the $2,300 allowed for the nomination. Redesignating the money for her Senate campaign and then using that money to pay vendor debts means contributors can exceed the $2,300 cap for the nomination. I didn't know about this, and I wonder how many other loopholes are out there.
UPDATE: NY Times sez it's unclear whether the money-shifting trick is legal.