A northern Virginia county is acknowledging that it underreported President Joe Biden’s margin of victory there over Donald Trump in the 2020 presidential election by about 4,000 votes. It was the first detailed accounting of the errors that initially became public as part of a criminal case. Thursday’s admission from the Prince William County Office of Elections comes a week after prosecutors dropped charges against the county’s former registrar. Counts were also off by lesser margins in a Senate and congressional race. In a statement, the county’s current director of elections emphasized that the mistakes did not come close to affecting the outcome of any race.