ABC News' David Wright Sen. Barack Obama called on his rival Sen. Hillary Clinton to release her recent income tax returns - a move the Clintons have long resisted.
Watch the VIDEO HERE.
Strapped for campaign cash, Clinton announced this week that she loaned her presidential committee $5 million of her own personal funds, but it was not immediately clear how she came by that much money.
"I've released my tax returns," Obama said today on his campaign plane, noting that Presidential candidates have a duty to be transparent and accountable.
He said, "The American people deserve to know where you get your income from."
Back when Bill Clinton was an office-holder, Hillary Clinton's business dealings were often a source of controversy. Remember the Whitewater land deal and all the scrutiny given to her client list at the Rose Law Firm?
Now that she is running for President,. Bill Clinton's finances are attracting attention.
He has cashed in since leaving the Oval Office - raking in a small fortune in speaking fees, as well as consulting for private clients and foreign governments. Fundraising for his Presidential library has also come under scrutiny.
In one recent controversy, he reportedly consulted with businessmen connected with the repressive government of Khazakstan. Some have criticized him for selling his credibility and, in the process, undercutting US foreign policy and his wife's public pronouncements.
Should Hillary Clinton use the former President's windfall to fund her own bid for the Presidency, it would inevitably become a campaign issue.
And, for her, there's another sensitivity. Given that she is making the case that she is an independent career woman, dipping into a rich husband's assets might undercut that image.
Nonetheless the Clintons have resisted frequent calls to open the library's books or release their income tax returns.
Pressed by reporters for his thoughts, Obama said "I don't have enough money to drop $5 million on a campaign."
Asked by email for reaction, Clinton campaign spokesman Howard Wolfson emailed back: "Senator Clinton discloses the sources of her income every year."
Clinton does file annual financial disclosure forms in connection with her job at the US Senate, but they are far less detailed than a joint tax return.
Wolfson added: "When will Senator Obama release the complete details of his relationship with Tony Rezko?"
Rezko, a Chicago businessman currently under indictment and facing trial later this month, was involved in a deal allowing Obama to purchase land adjacent to his house at below market value. Obama has, in retrospect, acknowledged the deal was "bone-headed."
Obama also recently returned some $150 thousand in campaign contributions from donors connected with Rezko.