LOUDOUN COUNTY, Va. — Loudoun County Supervisor Juli Briskman announced Tuesday that she will run for chair of the county Board of Supervisors, launching a campaign centered heavily on one of Northern Virginia’s most contentious issues: the rapid expansion of data centers. Briskman, who represents the Algonkian District, said controlling further data-center development would be a top priority of her campaign. Her entry creates the possibility of a Democratic primary contest w