IN ORDERLY Montgomery County, this year’s race for county executive is striking for having dwelt partly on which of the main candidates has more grossly mismanaged the place. That’s the core of the debate between the two politicians who have dominated Maryland’s biggest and richest county for the past 20 years and who are battering each other in this year’s Democratic primary: County Executive Isiah Leggett and his predecessor, Douglas M. Duncan. Each accuses the other of bungling the job. A third candidate, Phil Andrews, a veteran County Council member, says they’re both right.

In fact, the lineup does credit to the county: All three candidates in the June 24 primary are serious, substantive and civil, and no one doubts their competence or commitment. (A Republican attorney, James Shalleck, will face the Democratic nominee in November.)

Mr. Leggett, who served 16 years on the council before becoming executive in 2006, has been a steady and emollient leader through the upheaval of the recession. Mr. Duncan, who had the job for 12 years before that, was the driving force behind Silver Spring’s revival and the building of the Strathmore music center in Bethesda. Mr. Andrews, probably the council’s most respected member, has been an unwavering advocate for taxpayers and for fiscal restraint in the face of relentless spending pressure from interest groups.

The rap on Mr. Leggett and Mr. Duncan is that they were profligate spenders when times were flush, leaving the county in an untenable state when the economy collapsed. In both cases, it’s true — though more so for Mr. Duncan.

Preparing to mount a race for governor as his term wound down, he went on a three-year spree before leaving office in 2006 that drove up county spending by almost 30 percent. Pay and benefits soared for police, firefighters and other county workers as Mr. Duncan courted the public employee unions that represented them to support his gubernatorial candidacy.

Mr. Leggett followed suit when he entered office, signing more fat contracts with the county unions. Then the recession hit, and the county’s long-term commitments, which far outstripped those of other suburban jurisdictions, proved unsustainable. To his credit, Mr. Leggett was tough and skillful in retreating from those bloated contracts — in other words, solving a problem that was partly of his own making.

Characteristically, it was Mr. Andrews (Gaithersburg-Rockville) who most persistently called attention to the county’s overextended finances well before others recognized how perilous they were. Initially on the losing end of some 8-to-1 votes, Mr. Andrews’s views were ultimately vindicated as his council colleagues finally joined him in imposing some discipline on spending and sweetheart union deals.

Montgomery now has an enviably low rate of unemployment and is generally prosperous. At the same time, it suffers from high taxes and sluggish job growth. As they continue to slug it out over the past, it’s critical that the three candidates present voters with a compelling vision for the future.