With her campaign now officially suspended, Senator Hillary Rodham Clinton is confronting still another challenge: whittling down what is believed to be the largest presidential campaign debt in history.

Besides the $11.4 million of her own money that Mrs. Clinton lent her campaign, she had about $9.5 million in unpaid bills to vendors at the end of April, according to her most recent filing with the Federal Election Commission.

It is unclear how much debt she will ultimately report, because the campaign is still adding up the figures for May, which it must file to the commission by June 20. But Mo Elleithee, a campaign spokesman, said, “We don’t expect the debt number to look significantly different than it did on our last report.”

Other, far more affluent candidates have poured more of their own money into their presidential bids, like Mitt Romney, who spent more than $44 million in an unsuccessful run for the Republican nomination this year. His money was technically classified by his campaign as a loan, but it was clear from the beginning that he was simply self-financing a large part of his campaign.