A political action committee funded by Democratic mega­donor George Soros has spent nearly $1 million to promote progressive challengers in the Democratic primary races for prosecutor in Arlington and Fairfax counties, new campaign finance filings show.

The Justice and Public Safety PAC has donated about $583,000 to Parisa Dehghani-Tafti, a candidate for Arlington County commonwealth’s attorney, and $392,000 to Fairfax County commonwealth’s attorney candidate Steve T. Descano ahead of the June 11 primary, according to state figures released late Monday.

The donations represent the lion’s share of the roughly $744,000 and $546,000 the candidates, respectively, have raised to date.

Experts said the level of financing by a single committee may be unprecedented in a countywide race in Virginia and could refashion criminal justice in two of the state’s largest jurisdictions.

Quentin Kidd, director of the Wason Center for Public Policy at Christopher Newport University, said it was not long ago that spending $1 million on a state Senate race in Virginia raised eyebrows.

“This is a phenomenal amount to pump into a local race in Virginia, city or county,” Kidd said in an email. “I think it says a lot about the importance of criminal justice reform right now, and how important Virginia, and especially Northern Virginia, is as a political battleground and testing ground for reform ideas and arguments.”

The largesse of Soros’s PAC has allowed the challengers to outstrip the $191,000 and $251,000 hauls of incumbent Commonweath’s Attorneys Theo Stamos (Arlington) and Raymond F. Morrogh (Fairfax County), respectively. It has also given the challengers a major advantage in connecting with voters.

Dehghani-Tafti and Descano have been able to send more mailers and buy TV commercials in the expensive Washington-area market, which is not something that’s typical in local races for prosecutor in Virginia.

“Justice & Public Safety supports candidates with the experience and commitment to make their communities safer and fairer,” Whitney Tymas, chair of the Justice and Public Safety PAC, said in a statement.

Soros-funded PACs have donated heavily to prosecutors’ ­races in counties and cities across the country in recent years as part of a strategy to push liberal criminal justice policies. Local prosecutors wield broad powers over who is charged, what offenses they face and how long they serve in jail, so a reform-minded prosecutor can have a major impact on the system.

Dehghani-Tafti and Descano have tried to stake out positions to the left of the incumbents on bail reform, marijuana decriminalization, the death penalty and more. Stamos and Morrogh blasted their opponents for taking the money from a billionaire with no connection to Virginia.

“It really is a staggering amount of money and it’s remarkable to me,” said Stamos, who began the race with $29,000 left over from her previous campaign. “To suggest that [Dehghani-Tafti is] running a grass-roots campaign is laughable. She’s trying to buy the election, and I don’t think Arlingtonians are going to go for that.”

Dehghani-Tafti’s campaign manager, Michelle Woolley, said otherwise. “The idea that this election is being bought is fear­mongering, aimed at silencing questions of how [our] opponent runs her office,” she said.

Morrogh said such donations should not be allowed.

“In most states, this type of direct coordination between a campaign and a Super PAC would be illegal, and it should be in Virginia as well,” Morrogh said in a statement.

Dehghani-Tafti and Descano said the donations show their campaigns are moving in the right direction.

“Had we not spent the last year building that serious local campaign, we would not be getting any national support now,” Dehghani-Tafti said in a statement.

Descano welcomed the support.

“I think the level of investment by reform-minded groups shows just how high-priority of a race this is,” Jack Kiraly, campaign manager for Descano, said in a statement.