Three potential contenders for Richmond area seats in the General Assembly have been knocked out at the starting gate — at least temporarily.

Former Delegate Joseph D. “Joe” Morrissey and Dr. Derik E. Jones, son of Richmond Mayor Dwight C. Jones, are among the disqualified.

Both were blocked from challenging state Sen. Rosalyn R. Dance in a Democratic primary in the 16th Senate District that stretches from Richmond to Petersburg.

Meanwhile, David M. Lambert, son of the late former state Sen. Benjamin J. Lambert III, was cut from the Democratic primary race in Mr. Morrissey’s former House district, the 74th, which includes Richmond and the counties of Henrico and Charles City.

The Democratic Party labeled Mr. Morrissey, Dr. Jones and Mr. Lambert as ineligible to run in the June 9 party primary because each failed to submit enough signatures of registered voters from the respective districts in support of their names being placed on the ballot.

The decisions disqualifying the three were announced as the Democratic and Republican parties scrambled to finish certifying primary candidates by the deadline 5 p.m. Tuesday.

Party officials said Mr. Morrissey and Dr. Jones, a Richmond School Board member and pastor of First Baptist Church of South Richmond, fell short of the 250-signature requirement for Senate candidates, while Mr. Lambert did not muster the 125 signatures he needed to run for the House.

So, at this point, Sen. Dance and outgoing Petersburg Delegate Joseph E. Preston will be the only candidates in the Democratic primary in the 16th Senate district.

Meanwhile, with Mr. Lambert out, voters in the 74th House District will have to choose from three candidates in the Democratic primary: Stephen R. Adkins, chief of the Chickahominy Indian Tribe; Lamont Bagby, a Henrico School Board member; and the Rev. Leonidas B. Young II, a former Richmond mayor and ally of Mr. Morrissey.

Dr. Jones, who was deemed to have only 129 valid signatures out of the 297 he submitted, has been mum about the setback. Mr. Lambert, who was told only 83 of his 189 signatures were valid, said he is considering filing to run as an independent. “This would give me more time,” he said.

Typically, Mr. Morrissey is fighting back. If all else fails, he told the Free Press, he would run as an independent. “The voters deserve to make the choice,” he said.

However, at the Free Press deadline Wednesday night, he was considering a lawsuit to challenge the party’s claim that only 222 of the more than 1,000 signatures he submitted were valid.

Mr. Morrissey called it “astounding that more than 75 percent of the petition signatures were considered invalid,” calling it more evidence the party had “rigged the process against me.”

The decision to eliminate him and Dr. Jones was made by the Democratic Nominating Committee for the 16th Senate District, which included one representative for each of the six localities in the district.

Rather than review the signatures themselves, the committee relied on results produced by the office of Richmond Voter Registrar Kirk Showalter, who screened the signatures that Mr. Morrissey and Dr. Jones submitted on candidate petitions. Ms. Showalter’s office was acting unofficially.

Information is emerging that might lend some credence to Mr. Morrissey’s claim that he was wrongly bounced from the race.

According to the report the nominating committee received, many of the Morrissey and Jones signatures were deemed invalid because they didn’t include a date showing when the petition was signed.

Signatures on at least 10 sheets submitted by Dr. Jones were not counted because they lacked a date, according to Bettie Washington of Hopewell, chair of the nominating committee, who reported on the findings of Ms. Showalter’s office.

However, according to the published regulations of the Virginia Board of Elections, signatures cannot be discarded because a date is missing. Such signatures must be counted if other information on the petition sheet can show when the undated signatures were collected.

In 2012, courts twice put on a Richmond ballot candidates whom Ms. Showalter disqualified for not submitting sufficient valid signatures. One was a candidate for mayor and the other a candidate for the Richmond School Board.

Separately, five candidates qualified to run in the June Democratic primary in the 63rd House District, the seat Delegate Preston now holds and that Sen. Dance formerly held. The candidates are: Lashrecse Aird, a former legislative aide to Sen. Dance; the Rev. Larry Brown Sr., pastor of Gravel Run Baptist Church; William H. “Mouse” Jones Jr., a Petersburg businessman; Atiba Muse, a Petersburg School Board member; and Gerry Rawlinson, owner and operator of a health care business.

Also in the 69th House District in South Richmond and Chesterfield County, two Democratic primary candidates were certified: Incumbent Delegate Betsy Carr and a challenger, businessman and radio station owner Preston Brown.

Meanwhile, three other incumbent Democrats who represent Richmond are so far unchallenged for re-election: Henrico Sen. A. Donald McEachin and Delegates Jennifer L. McClellan and Delores L. McQuinn. Republican Delegate Manoli Loupassi, who also represents part of the city, also does not have a primary challenger at this time.