Delmon Young drove in the lead run and Domonic Brown added an insurance RBI in the eighth inning, as Philadelphia topped Washington, 5-3, in the middle test of a three-game series from Nationals Park.
Brown and Erik Kratz homered in the second inning and Jimmy Rollins added an RBI double for the Phillies, who recovered from a 5-2 loss in Friday's opener and won for the fifth time in their last eight overall.
"This is a big series for us. Every one is big, but this one especially since we're playing the Nationals," said Brown. "We're going out, working had and fighting. We're just having fun out there."
Chad Durbin (1-0) gave up one hit and recorded two outs in relief of Jonathan Pettibone, who worked six innings and allowed three runs on nine hits with six strikeouts.
Jonathan Papelbon tossed a scoreless ninth for his ninth save.
Adam LaRoche homered and drove in two, while Denard Span added three hits, an RBI and run scored for the Nationals, whose two-game win streak ended with their fifth loss in seven outings.
Drew Storen (0-1) was charged in defeat with two runs in the deciding frame. Dan Haren yielded four hits and three runs while fanning 10 in his six-inning start.
Storen walked Michael Young with one down in the eighth, and two batters later, a Delmon Young hit through the hole at second base was deep enough to allow the former Texas Ranger to make it 4-3. Michael Martinez came in as a pinch runner, and beat a throw home on a Brown double as Philadelphia went ahead by two.
Durbin allowed a bunt single to Kurt Suzuki and walked Tyler Moore, then retired Steve Lombardozzi on a liner before giving way to Jeremy Horst, but the Nats failed to make headway. Pinch-hitter Chad Tracy flied out and Span lined to right.
Ryan Zimmerman singled with one out in the bottom of the ninth and moved up on defensive indifference, but Papelbon fanned Bryce Harper swinging, LaRoche looking and Ian Desmond swinging to end the game.
"We left some guys on base, no doubt. We had some opportunities to score. They had some big two-out runs, and big two-out hits. We didn't," said LaRoche.
Brown and Kratz hit back-to-back two-out solo homers to give the Phillies a lead in their second turn against Haren.
Washington halved its deficit in the home third, as Span singled with one down, moved up on a Harper base hit, went to third on a Zimmerman liner and scored on a LaRoche single.
Lombardozzi came home on a two-out single from Span in the home fourth, but the Phils went back on top in the next half-inning as Pettibone doubled with two down and came in when Rollins followed with a double.
LaRoche tied the game in the home half on his one-out solo homer.
Philadelphia snapped a three-game losing streak in America's capital, earning its first win in the District of Columbia since Oct. 1, 2012 ... Brown has driven in at least one run in each of the last five games and 10 of his last 13 ... Prior to the game, the Nationals selected the contract of infielder/outfielder Jeff Kobernus from Triple-A Syracuse and designated pitcher Yunesky Maya for assignment.