At a recent rally, her largest to date, Hillary Rodham Clinton said that "the endless flow of secret, unaccountable money" must be stopped. A noble suggestion indeed.

But, just two weeks since the proclamation, the main super PAC backing Clinton's bid for the Democratic presidential nomination has accepted a $1 million contribution that cannot be traced.

Reports show that the pro-Clinton Priorities USA Action received the seven-figure donation on June 29. Additionally, the money came from Fair Share Inc. and Environment America Inc, two lone contributors to another super political action committee, called Fair Share Action according to records filed with Federal Election Commission, reports Associated Press.

Campaign and political contributions have in the recent past been a matter of intense scrutiny as they can involve "dark money." The two groups named in this particular case are nonprofits that are not legally required to reveal information about their donors.

"This appears to be an out-and-out laundering operation designed to keep secret from the public the original source of the funds given to the super PAC, which is required to disclose its contributors," said Fred Wertheimer, director of the Washington-based Democracy 21, according to CNS News.

While urging Priorities to return the money, Wertheimer said that Clinton should demand that the super PAC "publicly disclose all of the original sources of money" of any contribution it receives.

Priorities USA, rejected the suggestion and group spokesman, Peter Kauffmann, said the group is "playing by the rules," reported Chicago News. "In the face of a billion dollar onslaught by right wing groups, there is too much at stake for everyday Americans for Democratic groups to unilaterally disarm," he said.

Priorities USA raised about $15.6 million in the first six months of the year.

Several Republican candidates for president have nonprofits dedicated to helping their candidacies. These include Florida Sen. Marco Rubio, Former Florida Gov. Jeb Bush and Republican Texas Sen. Ted Cruz among others.