... Much of the battle will take place in the suburbs and exurbs of Northern Virginia -- Fairfax, Loudoun, and Prince William counties -- which have been the site of an ongoing population boom that includes young, Hispanic, and Asian-American voters. Over the next 20 years, about 30 percent of Virginia’s expected population growth will be in those three counties, according to statistics from the Weldon Cooper Center for Public Service at the University of Virginia.