Former employees of Rep. Tammy Duckworth who filed a workplace retaliation lawsuit against the Illinois Democrat are rejecting a settlement offer.

Their decision means the case will likely go to trial — scheduled to begin on Aug. 15, about three months before election day.

According to the Chicago Daily Herald, which first reported the news, the former employees, Denise Goins and Christine Butler, were offended by the response from Duckworth’s campaign following the settlement. The campaign called the lawsuit “a frivolous workplace case.”

“Within an hour of leaving the courthouse, her campaign decided to swing us through the mud again,” Butler told the Daily Herald. “So we emailed our attorney to let him know we want to proceed to trial.”

They told the newspaper that they weren’t pressured into rejecting the offer by the Kirk campaign. His campaign manager Kevin Artl told National Review the former employees called the campaign after the settlement, but said that they haven’t spoken to them about their decision to reject it.

Butler and Goins, who worked under Duckworth when she led the Illinois Department of Veterans’ Affairs, filed a lawsuit against her in 2009, alleging that they had been retaliated against for complaining about a supervisor.

Butler alleged that she was fired after filing complaints against her boss, but her termination was later reversed after a meeting with Duckworth. Goins claims she received a bad performance review and no raise after complaining about the same boss. She claims Duckworth told her to “do your job and keep your mouth shut” to keep her job.

Duckworth has denied that the employees were treated unfairly.

In June, Duckworth reached a settlement with the two, with an agreement between both sides that no law had been broken.

Duckworth was represented by the state’s attorney general’s office, who agreed as part of the settlement to pay the plaintiffs’ attorney fees and other court costs, which totaled $26,000.

In an email with Capitol Fax on Thursday, Maura Possley, who’s at the Illinois attorney general’s office, said that the settlement was binding, even though the former employees never signed the office’s standard form after the settlement.

The former employees’ decision to reject that settlement and head to trial could prove to be a political headache for Duckworth. Kirk’s campaign has raised the issue in their race. A web ad in May drew voters’ attention to a court hearing about the lawsuit.

Kirk is one of the most vulnerable Republican senators and faces an uphill battle in a Democratic-leaning state won by President Obama in both 2008 and 2012. The seat could be pivotal to which party controls the upper chamber.

Duckworth is set to address the Democratic National Convention in Philadelphia on Thursday.