CONTROL OF Virginia’s Senate appears to hinge on the outcome of a special election Tuesday for the seat vacated by Mark R. Herring, the state’s newly elected attorney general. The race in the 33rd Senate District, which includes Leesburg, Sterling, Herndon, Chantilly and other areas around Dulles airport, is a three-way contest, but there are only two serious candidates: Jennifer Wexton, a promising Democrat who has been a prosecutor and attorney in private practice, and Joe May, a moderate former Republican who served 20 years in the House of Delegates before losing a GOP primary last year. He is running as an independent.

Our pick is Ms. Wexton, who would bring to the job a refreshing dose of energy and passion, as well as valuable experience on mental health issues.

The third candidate, John Whitbeck, is a Republican best known for telling an anti-Semitic “joke” at a party rally last fall, then indignantly refusing to apologize for several days before being forced to do so by embarrassed fellow Republicans. (In damage-control mode, a robocall on his behalf now celebrates Mr. Whitbeck’s commitment to “diversity.”)

Mr. Whitbeck bitterly opposed the bipartisan transportation bill signed last year by former governor Robert F. McDonnell (R), a bill that will help get traffic moving again after a quarter century of funding paralysis. Now he says he fears the loss of transportation funding — the transportation funding he opposed — if Medicaid is expanded. This is incoherent. Mr. Whitbeck would be part of the growing Republican tide of conservatives whose allergy to compromise promotes deadlock.

Mr. May, who quit the GOP after hard-liners engineered Mr. Whitbeck’s nomination, is a successful local businessman. Decent, civil and knowledgeable about science and technology, he is a conservative who occasionally broke party ranks to support efforts to pay for better schools and roads.

A victory for either Mr. May or Mr. Whitbeck would hand control of the Senate to the GOP, since both would back Republicans for leadership posts. A victory for Ms. Wexton would leave the upper chamber with a 20-20 partisan split, which amounts to Democratic control since the tie would be broken by Lt. Gov. Ralph Northam, a Democrat.

While we admire Mr. May’s independence , his votes in favor of imposing gratuitous regulations on abortion clinics and impeding access to the polls by voters who lack certain forms of identification strike us as wrongheaded. He would oppose efforts by Gov. Terry McAuliffe (D) to expand Medicaid, which would protect hundreds of thousands of uninsured Virginians.

Ms. Wexton offers the most promising alternative. In addition to her stint as a prosecutor, she has worked on commitment hearings involving people who may pose risks to themselves and others, where she gained firsthand experience of the state’s mental health system. She supports common-sense background checks for gun buyers. She has taken to heart the desire of Northern Virginia voters that lawmakers break legislative logjams through compromise. That sounds like no big deal, but it has become a valuable commodity in Richmond.