Jennifer Wexton at a candidates forum on April 22 in Vienna, Va. (Jahi Chikwendiu/The Washington Post)

A COMPETITIVE primary field of well- ­financed Democrats is jockeying for the chance to run for Congress in Virginia’s 10th District, which, in addition to Loudoun County and parts of Fairfax and Prince William counties, in Washington’s inner suburbs, includes a rural swath extending through Clarke and Frederick counties to the West Virginia border. Among several plausible candidates, we support Jennifer T. Wexton. She is the best qualified and also the one most likely to chip away at partisan gridlock in Washington.

The winner of the primary, on June 12, will run against the incumbent, Republican Rep. Barbara Comstock, who is in her second term; she faces only nominal primary opposition.

Ms. Wexton, a state senator who represents chunks of Loudoun and Fairfax counties, was the lone former prosecutor and female lawyer among Democrats in Virginia’s legislature when she was first elected in a 2014 special election. As a Democrat in a legislature that was dominated by Republicans until this year, she has been noticeably successful in conceiving and enacting substantive bills. That, and her levelheaded bearing, have earned her bipartisan respect in Richmond.

The 40 or so measures she has pushed into law include legislation that makes online pedophiles easier to prosecute; empowers victims of revenge porn by allowing them to file lawsuits; regulates day-care centers; eases access to medication that prevents deaths from opioid overdoses; and codifies a woman’s right to breast-feed in public.

It’s ironic that Ms. Wexton, who used to make her living by putting criminals behind bars, has been attacked by some of her primary rivals for her alleged waffling on gun safety — apostasy in a Democratic primary. She is criticized for supporting a deal, struck by then-Gov. Terry McAuliffe, a Democrat, with the National Rifle Association, that forces domestic abusers to relinquish their firearms or face felony charges. It also encourages voluntary background checks by state troopers at gun shows, an option used by private gun sellers with increasing frequency since the massacre at a high school in Parkland, Fla., in February.

Those are victories for gun-control advocates and in line with Ms. Wexton’s general record in favor of bills to enhance gun safety. The price of those gains was that Virginia agreed to recognize the right to carry concealed arms for visitors from nearly all states that issue concealed-handgun permits; and Virginians with permits are granted reciprocal rights when they travel out of state.

That kind of compromise once greased the wheels of dealmaking in state legislatures and Congress but is now routinely squelched by partisanship and purity tests such as the one fellow Democrats are brandishing at Ms. Wexton. In fact, her stance is proof that she could help overcome polarization in Congress.

There’s much to admire in several of Ms. Wexton’s opponents, as we said. But if voters want a candidate who has proved she can win a tough election and then rack up genuine accomplishments while remaining true to progressive values, they have only one choice.