Del. Joseph D. Morrissey ran as an independent and won a special election to return to the House of Delegates. (Jahi Chikwendiu/The Washington Post)

Three African American residents of Virginia filed a lawsuit Friday contending that their constitutional rights were violated by the process recently used to pick a Democratic challenger to convicted Del. Joseph D. Morrissey (I-Henrico).

Morrissey was recently found guilty of a misdemeanor charge of contributing to the delinquency of a minor. In a special election Jan. 13, he won decisively against both a Republican and the Democratic Party’s chosen candidate.

The lawsuit, filed in federal court, argues that the Democratic Party, in its haste to distance itself from Morrissey, intentionally excluded African American voters from the process of nominating the challenger. African Americans make up about 60 percent of the House of Delegates district in question.

Morrissey, who was elected as a Democrat in previous races, has said he ran as an independent in the special election because he disagreed with the party’s method of nomination — also at issue in the lawsuit.

In addition to the misdemeanor conviction, Morrissey was accused in a felony indictment unsealed last week of submitting forged documents as evidence and lying under oath in the earlier case. He has denied any wrongdoing.

The lawsuit filed Friday adds to the controversy and uncertainty swirling around the decorum-bound General Assembly as it scrambles to find a way to punish or even expel Morrissey without offending the voters who elected him.

Although Kevin Sullivan, the candidate chosen by the Democratic Party, was defeated, one of the plaintiffs said the suit was filed to prevent the party from nominating a candidate in the same way again.

In bringing the suit, David Lambert, son of late longtime state Sen. Benjamin J. Lambert III, said he was following the example of his father.

“I’m following his lead,” Lambert said. “He always told me, ‘Do what’s right.’ This is what’s right.”

Lambert and the two others who filed suit — Gary Hill of Henrico and Linda Hill of Richmond — are represented by J. Paul Gregorio of Glen Allen.

Lambert said he plans to run in the June primary for the House of Delegates seat.

Through a spokeswoman, Robert Dempsey, executive director of the Democratic Party of Virginia, declined to comment on the lawsuit.

Paul Goldman, Morrissey’s law partner and a former Democratic state party chairman, said the lawsuit was assigned to Senior Judge Robert E. Payne of the U.S. District Court for the Eastern District of Virginia.

Morrissey’s decision to resign from the House, effective on the date of the election, and run for the seat left the party with just a few days to nominate its candidate through what the party calls an “unassembled caucus” and what others have called a “firehouse primary.”

In the end, about 40 people considered to be in good standing with the Democratic Party chose among three candidates, who paid $1,500 each to stand for the internal election.

The lawsuit argues that the method of nomination intentionally excluded African American voters living in the district, which includes the east end of Henrico County and parts of Charles City County and Richmond City.

The lawsuit says the party “feared this group of African Americans, who were not members of a local Democratic Party, might use their First Amendment rights to support a candidate the DPVA and other local party officials didn’t want to win the Democratic nomination. Therefore the firehouse primary rules were intentionally designed to disenfranchise them all.”

The suit, which also calls the fee illegal, says the party violated residents’ right to participate in the political process and their right to vote as well as the federal Voting Rights Act.

CORRECTION: An earlier version of this article gave an incorrect party affiliation for Del. Joseph D. Morrissey. This version has been corrected.