Jeannemarie Devolites Davis yesterday lost her bid for re-election to the Virginia Senate, dealing Republicans a blow in a key Northern Virginia district. John Chapman "Chap" Petersen, a Democrat, defeated Mrs. Davis in the 34th Senate District in central Fairfax. "This is one of those moments you dream of all your life," Mr. Petersen told the crowd last night at his postelection gathering at the Hilton McLean Tysons Corner. "When I was young and stupid, I thought I would put Fairfax on the map, but the reverse happened. The people of Fairfax City put me on the map," he said....