Martin O'Malley, former governor of Maryland, participates in the first Democratic presidential debate in October in Las Vegas. (Photo by Josh Haner/Bloomberg)

The struggling campaign of Democratic presidential hopeful Martin O’Malley took out a $500,000 loan in December to stay solvent and has had some staff working without pay, aides confirmed Sunday.

The loan was disclosed in a filing with the Federal Election Commission that also showed O’Malley’s fundraising during the past quarter to be a mere fraction of that posted by his two Democratic rivals, former secretary of state Hillary Clinton and Sen. Bernie Sanders (I-Vt.).

O’Malley, the former Maryland governor, reported receipts of $1.5 million, including the loan, during the three-month period ending Dec. 31, compared to $37 million for Clinton and $33.6 million for Sanders.

The loan was secured following O’Malley’s decision to participate in the public financing system, which provides matching funds for contributions of $250 or less but limits how much a candidate can spend overall and on individual state primaries and caucuses. In recent presidential cycles, most candidates have opted not to participate in the system because of those limits.

O’Malley spokeswoman Haley Morris said that O’Malley has received $900,000 in federal matching fund payments since Jan. 1, which aren’t reflected on the newly released report, and that the $500,000 loan has been paid off in full.

In November, O’Malley announced that he was redeploying much of his staff from his national headquarters in Baltimore to Iowa and other early states.

Morris said that some of the staff that remained in Baltimore, on both junior and senior levels, decided to forgo pay and continue working for O’Malley, a move she said “says a lot about the loyalty that he inspires in the campaign.”

It was not immediately clear how many staff were working without pay.

The report showed that as of Dec. 31, O’Malley had only about $169,000 in the bank and more than $35,000 in unpaid bills in addition to the $500,000 loan.

The disclosures came on the eve of Iowa’s first-in-the-nation caucuses. O’Malley has lagged far behind Clinton and Sanders in recent polls.