Editor's Note: There are just 21 days until Election Day, and the NBC News political unit each day will profile the most competitive races this midterm season.
Republican Rep. Frank Wolf served in this fast-growing, sprawling D.C. exurban district for over 30 years before announcing his retirement last year. A recent redistricting in 2012 shifted the district towards the GOP -- and Mitt Romney narrowly won it over Barack Obama – so Republicans feel they’re well positioned to hand Wolf’s seat off to one of his former aides, state Delegate Barbara Comstock. A former RNC oppo researcher and Oversight panel lawyer known for digging up dirt on the Clinton family and Al Gore, Comstock is widely admired in her own party and reviled by her old 1990s foes. She faces Democrat Fairfax County Supervisor John Foust, who’ll try to paint her as too conservative for D.C.’s wealthy and diverse inner suburbs. The Democratic Congressional Campaign Committee recently canceled a TV ad buy for Foust, suggesting that the GOP has the advantage in this race.