John Vihstadt, the incumbent and independent candidate running for Arlington County Board, greets Arlington resident Michael Jackson, at the Columbia Pike farmer's market, October 19, 2014, in Arlington, Virginia. (Evelyn Hockstein/For The Washington Post)

BY ALMOST any measure, Arlington County is a local and national success story, having remade itself over two decades — with a big assist from Metro — from a green but sleepy suburb into a still green but diverse, dynamic and highly desirable set of communities. Lately, the political comity that helped guide that transformation has frayed amid a bitter debate over a proposal to build an expensive streetcar line on fixed tracks along Columbia Pike.

That debate headlined a special election last spring to fill a vacancy on the five-member County Board and is dominating a rematch for the same seat in Tuesday’s general election. We support the incumbent, John E. Vihstadt, a badly needed independent voice in a heavily Democratic county.

Mr. Vihstadt, a lawyer with decades of involvement in community affairs, has opposed the streetcar project. His opponent, Democrat Alan E. Howze, also a very capable candidate, supports it.

We happen to agree with Mr. Howze that the streetcar would yield long-term economic benefits and added passenger capacity that buses — even expanded ones — cannot replicate. However, there are other compelling reasons for reelecting Mr. Vihstadt, who, on his own, cannot erase the current 3-to-2 pro-streetcar majority on the board. (In addition to Mr. Vihstadt, Democrat Libby Garvey opposes the project.)

Mr. Vihstadt, a longtime Republican running now as an independent, has made the case against the streetcar project in a civil and cogent way, arguing that the long-term benefits — which he doubts — do not justify what he considers to be its exorbitant cost ($333 million for the 4.5-mile portion on Columbia Pike, plus another $165 million or so for another segment along Route 1) and its potential to worsen traffic along Columbia Pike. Clearly, many Arlingtonians believe he’s right.

Much of the county’s Democratic establishment, including Mr. Howze, disagrees, citing a consultant’s estimate that a streetcar would generate $2 billion to $3 billion more in benefits than would improved bus service over a 30-year period, plus several thousand additional jobs. We’ve seen nothing to cast serious doubt on the consultant’s numbers.

Nonetheless, many Democrats have accorded Mr. Vihstadt grudging respect as someone who formulates and presents his views intelligently; he is no tea party bomb thrower. Equally important, in our view, is his insistence that the county reevaluate other expensive projects, such as a proposal for a state-of-the-art aquatic center, which he regards as unaffordable.

Whether Mr. Vihstadt prevails or not, it’s important for Arlington to have the debate; without him, the board runs the risk of groupthink.

Arlington voters will also fill two seats on the school board. Nancy Van Doren, appointed in September to fill the vacancy when Noah Simon resigned, is running unopposed to fill the rest of a term that ends Dec. 31, 2016. In the contest for a four-year seat between Audrey R. Clement and Barbara J. Kanninen, we favor Ms. Kanninen because of her broad experience in children’s issues. An economist and children’s book author with children in the public schools, Ms. Kanninen wants to enrich the curriculum and attack the achievement gap while understanding the need to bring new thinking to the fast growth that is straining the system. The races are nonpartisan.