With results available from 25 of the county's 26 precincts on Wednesday, two-term Assistant Judge Patricia Duff had 1,540 votes, and challenger Paul Kane had 1,289. Incumbent Assistant Judge Lamont Barnett was running a distant third with 899 votes.
Duff, of Brattleboro, and Kane, of Westminster, will move on to the general election.
No Republicans had run for the office, while Liberty Union candidates Alice Landsman and Lynn Russell were unopposed.
Assistant judges serve four-year terms and can sit as finders of fact with presiding Superior Court judges in family and civil cases. They also are county administrators with responsibilities including appointing a clerk and treasurer; developing a county budget; and maintaining county property.
In Windham County, the assistant judges maintain the historic Newfane courthouse and the sheriff's office across Route 30.
The assistant-judge position, which is part-time and normally low-profile, had attracted some attention this year: Duff and Barnett ran as an incumbent team, but Kane lobbied hard for the office.
Duff had said her experience is an asset. She talked about maintaining the historic character of the courthouse and said the assistant judges are working to establish a supervised-visitation center for children in Brattleboro.
Barnett, of Rockingham, was appointed to the position in 2012 to fill a vacancy and said he had sat on the bench for more than 2,000 hours. He is a past chairman of Rockingham Selectboard and had chaired the Windham County Democratic Committee.
Kane has experience with the court system as a former probation officer and supervisor with the Vermont Department of Corrections. He also was a social worker with the state Department for Children and Families.
Kane had said he would like to help bring a specialized drug court to Windham County.
Mike Faher can be reached at firstname.lastname@example.org or 802-254-2311, ext. 275. Follow him on Twitter @MikeReformer.