The Virginia House of Delegates in 2015. (Bob Brown/Associated Press )

THREE NORTHERN Virginia seats in the General Assembly — one in the state Senate and two in the House of Delegates — are coming open in the fall elections, and Democrats are holding primary contests June 9 for all of them. The following are The Post’s endorsements in those races. (A Republican primary is being held in District 2, which encompasses part of Prince William and Stafford counties. The Post makes no endorsement in that race.)

●State Senate District 29: Prince William County, Manassas and Manassas Park. The Democratic incumbent, Charles J. Colgan, who has held the seat since 1976, is the longest serving state senator in Virginia’s history. His retirement after 10 terms touched off a primary race featuring three plausible candidates, each of whom ran for the House of Delegates two years ago.

The strongest of them is Atif M.Qarni, who served eight years in the U.S. Marines, including a tour in Iraq, before becoming a school teacher in Prince William County.

Mr. Qarni, widely admired for his energy, determination and commitment to service, would be the only active teacher in the Senate. He’d also be an effective advocate for schools who could speak to the real-world impact of legislation and policy from the perspective of someone working in one of the most diverse school districts anywhere.

●House of Delegates District 44: Alexandria area of Fairfax County. A pair of Democrats are on the primary ballot in this heavily Democratic district, where no Republican ran in 2013 against the incumbent, Scott Surovell. He has now mounted a campaign for the state Senate.

One of the candidates, Paul E. Krizek , senior executive at a charitable nonprofit organization, is abundantly qualified to serve in Richmond, having been heavily involved in local civic groups for more than two decades. Mr. Krizek, also a longtime Democratic Party activist, says his focus will be transportation improvements in the Route 1 corridor, a sensible priority in a district badly clogged with traffic.

His opponent, Justin M. Brown, has wide experience with veterans’ issues from his years as a staff member on Capitol Hill. But his background in state and local matters is scant compared with Mr. Krizek’s.

●House of Delegates District 45: Along the Potomac from south Arlington, through Alexandria and into southern Fairfax County. With the departure of the incumbent, Del. K. Robert Krupicka Jr., five candidates jumped into the primary in this solidly Democratic district. Our choice is Craig T. Fifer , who has the background and skills to make an exceptional member of the state legislature.

Mr. Fifer, chief communications officer for Alexandria, has broad knowledge of local and state issues and has won praise from incumbents for his detailed command of complex legislation. He is widely regarded as an authority on questions of open government, technology and access to public information, and he has a knack for clear and concise presentation.

In addition to his long government service, Mr. Fifer also has extensive hands-on experience as an advocate for abused children in the court system. That background, combining policy savvy and on-the-ground experience, is excellent preparation for a legislator.