A group of African Americans seeking to overturn Maryland’s congressional map on grounds that Gov. Martin O’Malley (D) and the state legislature racially gerrymandered lines to help elect Democrats won an initial victory in court Monday.

U.S. District Judge Roger W. Titus rebuffed an argument to dismiss the case from Attorney General Douglas F. Gansler (D) and sided with the group that a three-judge panel should be seated to hear the case.

Titus said he would immediately notify the chief judge of the U.S. Court of Appeals for the Fourth Circuit. The chief judge could still decide not to grant a three-judge panel, but the development suggested the state may have to fully justify its map before the court.

O’Malley and the state’s Democratic controlled legislature significantly altered lines in Montgomery County, drawing on the Washington region’s surging minority population to make the district held by the state’s senior Republican, Rep. Roscoe Bartlett, majority Democrat. Plaintiffs argue that in doing so, Democrats also diluted to voting strength of minorities.

If the plaintiffs next get their way, the timing of Maryland’s April 3 congressional primary could become an issue. The plaintiffs, who are backed by the Fannie Lou Hamer Political Action Committee and Republicans, want a trial to begin in January.

Maryland’s Board of Elections has said a decision on the legality of the map must be reached by mid-December or there could be delays in holding the primary. The state needs several weeks in January to format its ballots and must meet a federal mandate to send the ballots to troops overseas by early February.