Jennifer Wexton is a candidate running in the Democratic primary for Virginia’s 10th Congressional District. (Dayna Smith/For the Washington Post)

Virginia Gov. Ralph Northam on Thursday endorsed state Sen. Jennifer T. Wexton, one of seven Democrats running for the party’s nomination to challenge Rep. Barbara Comstock (R) in a congressional race targeted by both major parties.

Northern Virginia’s 10th District is expected to be among the most competitive in the nation.

The district includes Loudoun County and parts of Fairfax and Prince William counties, as well as Clarke and Frederick counties to the west. As the closest thing to a battleground district in the region, it attracts more than its share of activists and donors. It’s a swing district long represented by a Republican in the House, despite consistently being won by Democrats in statewide and national races.

Northam’s support could give Wexton (Loudoun) a boost in the district, which he won easily in last year’s gubernatorial election — widely seen as a referendum on President Trump. In the 2016 elections, Trump lost in the district by 10 points, despite Comstock winning it by six.

Northam presided over the state Senate as lieutenant governor during Wexton’s Senate service.

“I saw her tenacity on the Senate floor where we fought together to expand Medicaid and stood up to the gun lobby,” Northam said in a statement. “From the Virginia Senate to my campaign for Governor, Jennifer Wexton has always had my back and I know she will fight even harder for Northern Virginia families.”

The National Republican Congressional Committee framed the endorsement as an attempt to salvage Wexton’s campaign, which is among the top highest fundraisers but not first in the crowded field.

“The establishment is swooping in to try and save Jennifer Wexton’s failing primary bid,” NRCC spokeswoman Maddie Anderson said. “Governor Ralph Northam endorsed Wexton in the latest desperate attempt to make her relevant.”

Wexton, the only elected official running in the Democratic primary, is a former prosecutor with roots in Loudoun County, where most Democrats in the district live.

Her biggest competition in the primary comes from anti-human-trafficking activist Alison Friedman, Army veteran Dan Helmer, former federal prosecutor Paul Pelletier and communications strategist Lindsey Davis Stover.

Physician Shadi Ayyas and scientist Julia Biggins are also running. Deep Sran, an educator, dropped out of the race last month.

Helmer and Stover’s campaigns said they respect Northam but downplayed the endorsement, saying voters’ opinions are the ones that matter most.

Through her campaign manager, Friedman said the endorsement was not a surprise.

In addition to Northam, Wexton was endorsed by Democratic Reps. Gerald E. Connolly and A. Donald McEachin.

“I have seen firsthand the dedication the Governor has to the people of Virginia,” Wexton said in a statement, “and I look forward to continuing our partnership to better serve Virginia families when I am in Congress.”