A coalition of individuals and groups says it was targeted by an overzealous Justice Department under President Trump in a lawsuit filed on Friday, challenging the $1.8 billion fund the president said would be created for victims of a “weaponized” federal government.

The lawsuit presented a novel approach to challenging the fund, which legal experts have warned could be hard to fight in court because of the difficulty of pointing to an individual or group directly harmed by the fund. It followed an earlier lawsuit brought this week by two law enforcement officers who were present during the Jan. 6, 2021, attack on the Capitol and said they faced violence, only to see rioters now floated as possible settlement recipients.

The Trump administration has left little doubt that the fund is designed to steer money toward many of Mr. Trump’s supporters, including those convicted of breaking the law on the president’s behalf. The lawsuit filed Friday claims that explicit partisan favoritism, alone, could make the fund illegal.

“By its own terms, the anti-weaponization fund is available only to claimants who assert that they were targeted by ‘Democrat’ administrations, even though the current administration has weaponized the awesome power of the federal government against its perceived political opponents like no other administration before it,” the lawsuit said. “Neither the First Amendment nor the equal protection guarantee of our Constitution countenance such blatant partiality.”

The plaintiffs joining together in the case include a diverse mix of people and groups who the lawsuit said were targeted by the Trump administration or would be negatively affected by the fund.

They included Andrew Floyd, a former federal prosecutor who has said he was fired for his work on the Jan. 6 investigation, as well as Jonathan Caravello, a professor in California who was arrested while protesting an immigration raid, charged with felony assault of a federal officer and later acquitted by a jury.