The federal investigation into D.C. Mayor Vincent Gray's campaign is unlikely to conclude before next summer after a federal judge postponed a hearing for a woman who helped implement the illegal, off-the-books shadow campaign that boosted Gray's prospects.

Jeanne Clarke Harris, who served as a communications consultant to Gray's 2010 campaign, was scheduled to appear in U.S. District Court for a status hearing Monday, but Judge Colleen Kollar-Kotelly agreed to delay it until March because prosecutors said they weren't ready to set a sentencing date. The postponement means it's unlikely Harris will face sentencing before June.

In a written motion, Harris' lawyer, Mark Tuohey, wrote that his client had "cooperated fully with the government."

Prosecutors also agreed to the motion.

Although she was the third person linked to Gray's campaign charged in connection to the probe, Harris' case is perhaps the most critical to the future of the investigation.

According to court papers, Harris helped implement a $653,800 shadow campaign that was intended to prop up Gray's citywide bid against Adrian Fenty, the then-mayor and Gray's political rival.

Harris pleaded guilty to conspiracy, fraud and false statements and a local campaign finance violation.

But while Harris played a significant role in the execution of the shadow campaign, she was not responsible for designing or funding the secret operation.

"The money was from co-conspirator No. 1, but the plan was developed by another person," Harris said during a July court appearance.

People familiar with the investigation have identified co-conspirator No. 1 as Jeffrey Thompson, a major city contractor and campaign donor.

Thompson has not been charged, and his attorney has declined to comment.

The ruling in the Harris case marked the second time in a week that Kollar-Kotelly approved plans that will extend the life of the investigation.

Last week, Kollar-Kotelly sided with prosecutors when she overruled a request from a lawyer for Thomas Gore, the Gray's campaign assistant treasurer, to schedule sentencing in his case.

Gore pleaded guilty in May to a federal count of obstruction of justice and three District counts of helping to make campaign contributions in the names of others.