CLOCKWISE FROM TOP LEFT: Lindsey Davis Stover, Paul Pelletier, Jennifer T. Wexton, Julia Biggins, Dan Helmer and Alison Kiehl Friedman. (Jahi Chikwendiu/The Washington Post/Jahi Chikwendiu/The Washington Post)

Never before have Democrats in Northern Virginia had more than one, let alone six, serious candidates for the nomination to challenge Rep. Barbara Comstock (R-Va.).

There’s the party establishment darling, the strategist, the biggest fundraiser, the Army veteran, the federal prosecutor and the scientist.

A crowded primary is exciting for activists but poses both a challenge and an opportunity for candidates, who may not need a majority to win on June 12 but must turn out enough of their supporters to win a plurality.

In this six-way primary, in what is expected to be one of the most competitive House races in the country come November, each candidate has a carefully tailored message intended to appeal to a certain slice of the electorate.

“The one who works the hardest is going to do the best, there’s no question,” said Jim Moran, a Democrat who represented a neighboring district in Congress for more than two decades. “If you’ve organized, you’ve got your supporters, and they know who to get out to the polls on primary day. I think it’s still up for grabs.”

The candidates with the ­money to run TV ads in the district, which is part of D.C.’s pricey media market, are state Sen. Jennifer T. Wexton (D-Loudoun), former Obama administration official Lindsey Davis Stover, anti-human trafficking expert Alison Friedman and Army veteran Dan Helmer.

Rep. Barbara Comstock (R), is running for a third term from a Northern Virginia district considered one of the most competitive in this fall’s midterm elections. (Katherine Frey/The Washington Post)

Former federal prosecutor Paul Pelletier and infectious disease scientist Julia Biggins have fewer resources but are running on the strength of their professional accomplishments and performances at public forums.

The pressure is on for the party to field a candidate who can compete with Comstock, a tenacious campaigner who is seeking a third term but is nonetheless vulnerable in a blue wave. Her seat is one of 23 held by Republicans that Democrats must flip to win control of the House.

Rep. Seth Moulton (D-Mass.), the featured speaker at Fairfax County Democrats’ annual fundraising dinner this month, led the crowd in a chant of “goodbye.”

“This is important because it’s what every one of us is going to have to say to my friend Barbara Comstock in November,” he said to applause.

First, Democrats must choose a nominee.

Although most voters won’t start paying close attention until the final days of the campaign, the candidates have attended a marathon of forums, flooded mailboxes with literature and deployed an army of door knockers.

“A lot of it comes down to who has the energy to go to every forum, every gathering,” said Mark J. Rozell, dean of the Schar School of Policy and Government at George Mason University. “In these relatively low-turnout primaries, it is often who [voters] know and who they have seen who gets them motivated.”

Wexton is relying on existing support from Loudoun voters in her legislative district, which partially overlaps with the sprawling congressional district, stretching from the D.C. suburbs to the Shenandoah Valley.

Once considered reliably Republican, the 10th District has grown friendlier to Democrats as more immigrants and federal workers have moved in.

The district includes Loudoun, where the population nearly doubled in the 1990s and ballooned to more than 375,000 by 2015, according to census data. It is among the richest counties in the nation and family-focused — about half of the households have children.

Voters driven by their animus for President Trump helped Gov. Ralph Northam win the district by 11 points last year and gave Democrats reason to believe Comstock could be beat.

The six Democratic primary hopefuls are targeting about 45,000 voters who turned out for Northam’s primary against Tom Perriello, who ran to his left.

Voters in the 10th District chose Hillary Clinton over Sen. Bernie Sanders (I-Vt.) and Northam over Perriello — a good omen for Wexton, the establishment favorite.

She has the endorsement of Northam and Rep. Gerald E. Connolly, a fixture in Fairfax County, as well as the Service Employees International Union and the Coalition to Stop Gun Violence.

Wexton is deeply rooted in Loudoun, where she was a prosecutor and, with her husband, has raised two children.

During her four years in the legislature, she passed bills to curtail opioid addiction, regulate day-care centers and prosecute online child sex offenders — issues that appeal to suburban female voters who helped Northam win.

She also talks about passing more than 40 bills through a GOP-controlled legislature, a nod to bipartisanship that could resonate with general election voters.

“Wexton, from an ideological standpoint, is a perfect fit for that district,” said Senate Minority Leader Richard L. Saslaw (D-Fairfax), who backs her. “She’s a liberal but not to the point where it’s going to scare off the slightly moderate to conservative voters. Jennifer’s damn sensible.”

Other primary hopefuls have tried to weaken Wexton.

While door knocking, Friedman tells voters that unlike “the other person who’s considered a front-runner,” meaning Wexton, she has been “unequivocal” in her opposition to the NRA.

Friedman and Helmer both criticize Wexton’s vote to allow guns to be transported in an unlocked car glove box, which then-governor Terry McAuliffe vetoed, and her support for a bipartisan compromise on guns brokered by McAuliffe that expanded concealed-carry rights.

Friedman, by far the largest fundraiser with a war chest of almost $1.4 million, is stressing gun control and launched the first TV ad of the race with a message tailored toward parents.

And, based on her past work at the State Department, she’s making a pitch aimed at federal workers who live in the district.

“I have spent my life fighting for equality and justice — so I can’t just sit by while our most vital institutions of democracy are under attack,” reads one of her fliers.

Stover, who was a senior adviser in Veterans Affairs and chief of staff to a Texas congressman, is betting her 12 years of federal experience and personal story will appeal to voters upset by Hillary Clinton’s loss.

“I know what it’s like to work three minimum-wage jobs and barely make ends meet,” she said at the Fairfax dinner. “I know what it’s like to have over $80,000 in student loans. I also know what it’s like to charge groceries because you can’t afford to pay for it otherwise.”

The message is intended to resonate with low-income voters in Manassas, Manassas Park, Prince William and the western part of the district, Clarke and Frederick counties as well as Winchester, but also educated professionals who can barely afford to live in tony parts of Fairfax and Loudoun counties.

Her campaign manager, Emma Brown, came to Stover fresh from helping a Democrat unseat a Republican state lawmaker in the western part of the district; she reactivated her networks for Stover.

Helmer has a résumé that plays well in a district home to lots of active-duty military personnel, veterans and law enforcement.

A U.S. Military Academy graduate, a Rhodes scholar, the son of an immigrant and the grandson of Holocaust survivors, Helmer served combat tours in Iraq and Afghanistan and is still a lieutenant colonel in the Army Reserves.

He has the endorsement of VoteVets, an organization committed to electing more veterans to Congress, which backed Moulton, Rep. Anthony G. Brown (D-Md.) and newly sworn-in Rep. Conor Lamb (D-Pa.).

“People feel like if you’ve served your country and you’ve been to war, you’ve got a strong personality, and you’re prepared to stand up to Donald Trump,” said Jon Soltz, an Iraq War veteran and co-founder of VoteVets.

Helmer, who calls for Trump’s impeachment, tells voters he has seen the consequences of military action: “It’s inscribed on the headstones of dear friends.”

His military background gives him instant credibility on gun control, a position he highlighted recently in an undercover video in which he legally purchased a semiautomatic rifle — like the one he carried in the Army — without a background check from a private dealer at a gun show.

Pelletier is running as a law-and-order candidate. As a federal prosecutor for almost three decades, he directed the public corruption investigation of lobbyist Jack Abramoff and seized more than $200 million from secret accounts of a Colombian drug lord, which at the time gave Pelletier a Guinness world record.

He likes to say Comstock should be prosecuted “for aiding and abetting” Trump.

“In many ways, I believe I’m their worst nightmare,” he said at a Winchester forum.

To introduce himself to voters, he is holding nine town hall meetings throughout the district. The strategy is backed by mail, door knocking and phone calls.

Biggins is relying entirely on her unabashedly liberal message and ideas to convince voters to elect a female scientist to the House. A Manassas resident, she is the only candidate who lives outside Fairfax and Loudoun counties.

She has the endorsement of the Northern Virginia chapter of Our Revolution, the group Sanders started after his presidential bid.

Biggins, who supports single-payer health care, is the only candidate who talks about the need to add not just more female, minority and LGBT lawmakers to the House, but also more teachers, engineers, farmers and laborers. Her logo incorporates a microscope, and her website features a photo of her in a white lab coat.

“We’re governed by a professional political class made up of lawyers, lobbyists and aides who are dismissive of data, scared of transparency and more interested in saying the right thing than doing the right thing,” she said recently. “And that’s why I am running for Congress. To do the right thing.”