Mayor Vincent Gray’s 2010 campaign used hundreds of thousands of dollars in undocumented donations to help him get elected, a secret effort that the top District prosecutor said “compromised” the election.

Jeanne Clarke Harris, 75, admitted in city court to hiding and doling out $653,800 from the pockets of a well-known political donor and government acontractor, The Washington Post reported Tuesday.

Harris testified that she used money from a local donor – who The Post reported to be D.C. businessman Jeffrey Thompson – but that the donor did not know about the scheme.  A third, unidentified person then devised the details, she testified.

Prosecutors did not claim Gray had knowledge of the secret fund, but Harris said the effort was “coordinated” with members of his campaign.

After hearing the plea, U.S. Attorney Ronald Machen Jr. denounced the legitimacy of the 2010 election.

“The mayoral campaign was compromised by backroom deals, secret payments and a flood of unreported cash,” Machen said to reporters. “The people of this city deserve better. They deserve the truth.”

The money paid for about 10,000 yard signs, 5,000 T-shirts, banners, lapel stickers and posters designed to look like part of the official campaign. The contribution also funded 200 umbrellas, consultants, canvassers, drivers, laptops, radios and a public address system.

The plea comes on the heels of continued suspicion about the corrupt 2010 election. In March 2011, a team appointed by the U.S. House of Representatives investigated claims by former mayoral candidate and ex-D.C. employee Sulaimon Brown that Gray paid and promised him a job if he bashed Fenty during the race. Later that year, a D.C. Council report slammed the alumnus in for allegedly having shady hiring practices and paying his top officials sums above legal limits.

The congressional probe later dismissed wrongful hiring allegations against Gray in November 2011, citing Brown’s lack of credibility.

The probe into Gray’s suspected ‘shadow campaign’ began in March.