WASHINGTON -- The split crowd of 34,789 at Nationals Park went back and forth Monday, but every time the Nationals attempted to establish themselves in their home ballpark against their National League East rivals, Philadelphia responded.
Washington could not hold its lead against Phillies starter Roy Halladay, and lost its sixth consecutive game against the Phillies, 5-4.
"We hung in there today. Those are the Phillies -- they're in first place in our division," said first baseman Michael Morse, who homered in the second. "It just shows you we have a good team and when we get things rolling, we can hang with anybody."
Lefty Sean Burnett relieved Livan Hernandez in the seventh to face the Phillies' lineup of three consecutive left-handed hitters. He walked Chase Utley, allowed an RBI single to Ryan Howard and surrendered a sacrifice fly to Raul Ibanez to give Philadelphia the lead.
"It's hard to walk away from this one," said Burnett, who took his second loss of the season. "Livo threw another good game, and our offense put up four on Halladay, which isn't going to happen too much. It's a game you have to win, and we had it won if I could execute and get the lefties out that I'm supposed to."
Hernandez pitched into the seventh, but he labored through the fourth, which included the Phillies' first back-to-back home runs of the season.
Howard led off the inning with a homer to right field and Ibanez followed by depositing a home run into Washington's bullpen. Carlos Ruiz followed with a double and scored on a Domonic Brown single to take a temporary lead.
Second baseman Danny Espinosa quickly tied the game in the fifth with his eighth long ball of the year, which increased his team-best RBI total to 29.
The Nationals' first of three homers came courtesy of Morse, who sent a 1-2 fastball from Halladay into the left-center stands in the second inning for his fifth home run in the past seven games.
"The first two I thought were really good pitches," said Halladay, who went seven innings in the win. "Morse was in, maybe even off the plate a little bit. Espinosa was a changeup down and in where we wanted it, and he kind of golfed it."
Washington scored another second-inning run on a Hernandez sacrifice bunt, and after he lost that lead, Laynce Nix returned it by sending Halladay's first offering of the sixth into the right-field stands.
"There's no moral victories, but you hope it seeps into people that we can do this, we can hit," said manager Jim Riggleman. "We know we can hit. We have a history of hitting and we're going to hit. When you go out and do it against a Cy Young guy, that should certainly reinforce it if there's any doubt creeping in."
But the Philadelphia fan who caught Nix's homer -- and likely serenaded Jayson Werth with cries of "Jay-son! Jay-son!" throughout the game -- threw the ball back onto the field.
The Nationals' lead was equally short-lived, and although they threatened with two on and no outs in the seventh, Werth struck out swinging to end the threat and return control to Philadelphia.
"If you're playing great and staying in the game, it just doesn't add up. At the end, you want to win," said Alex Cora, who made the first out of the seventh in a rundown after Rick Ankiel hit a grounder back to Halladay. "We're playing great, but at the end of the day, it's not about hitting or not hitting, making plays or not making plays. It's about who has more runs on the scoreboard, and that hasn't happened for us lately."
Steven Miller is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.