David Blair at a forum on April 27 in Washington. (Bill O'Leary/The Washington Post)

THE DEMOCRATIC primary race for county executive, the top local office in Montgomery County, Maryland’s largest jurisdiction, has assumed a slightly surreal aspect.

One leading candidate declared he’d rather divert jobs to neighboring Frederick County than attract them to Montgomery, which desperately needs to expand its tax base to maintain its highly rated public schools and services. Another unleashed a ludicrous attack ad on cable TV, likening a rival — and fellow liberal Democrat — to President Trump.

Meanwhile, the target of that ad, David Blair, whom we endorsed, has run an insistently positive, upbeat and serious campaign. His platform is coherent, his messaging disciplined and his thinking strategic. The fact that he happens to be self-funding a major portion of his campaign — he founded, ran and sold a pharmacy benefits management company — has prompted most of his opponents to use his wealth as a cudgel against him.

The county is a sophisticated place, and voters tend to be highly educated; it’s a fair bet most will not resent Mr. Blair’s success in business. A more cogent critique is that he lacks government experience. That’s true, though in the business world he dealt with state governments routinely. In this race, however, the more relevant point is that Mr. Blair makes the most convincing case for his ability to attract jobs and spur economic vitality in a county of 1.1 million people whose prospects look shaky, despite a national and regional economic boom.

Plenty of Montgomery voters, weary of traffic, are skeptical of additional development. The county has added nearly 100,000 residents since 2010. The winner of the primary — which, given the Democrats’ dominance in the county, is tantamount to the election — will have to manage new projects carefully, minimizing the impact on school crowding and roads.

Yet it is folly to suppose that erecting impediments to growth, particularly commerce and jobs, is a path to success. Without vibrant new businesses and the revenue they produce, the county, already desperate for funds, will be forced to trim spending on public education, affordable housing, health services and other amenities that residents expect. That’s a recipe for long-term decline.

One leading candidate for the job, Marc Elrich, a veteran at-large member of the County Council known mainly for opposing development projects of every description, recently suggested just such a strategy. In a telling interview with the website Greater Greater Washington, he said his solution to roads clogged with commuters is to focus employment elsewhere. “I prefer to put jobs in Frederick” County, he said.

That’s a fine point of advocacy for a candidate running in Frederick. It fails as a selling point in Montgomery. So does the recent ad paid for by Roger Berliner, another incumbent council member running for county executive, comparing the civil, substantive, detail-oriented Mr. Blair to Mr. Trump.

A better comparison is Rep. John Delaney, a Democrat who, like Mr. Blair, was a successful businessman without government experience when he first ran for Congress six years ago in Maryland’s 6th District, which includes part of Montgomery. Mr. Delaney has been an excellent member of Congress. We think Mr. Blair would be similarly successful as county executive.