Esa Lindell scored for Dallas (44-21-4), which is second in the Central Division, eight points behind the Winnipeg Jets and three ahead of the Colorado Avalanche. Jake Oettinger made 22 saves.
"[Philadelphia] worked hard. They played a hard game," Dallas forward Jamie Benn said. "It was just one of those games where there's really not that much out there and we found a way to get it done. Made some good plays when they were there and remember what we can learn from. Two points is what we came here for."
Travis Konecny and Ryan Poehling scored for Philadelphia (28-34-9), which has lost four straight (0-3-1), and is 10 points behind the Montreal Canadiens for the second wild card into the Stanley Cup Playoffs from the Eastern Conference. Ivan Fedotov allowed two goals on three shots in the first period before Ersson (16 saves) entered in relief at the start of the second period.
"I thought we clogged them up well and took away what they wanted to do and how they received and created a lot of offense there, we could have had a lot more," Poehling said. "I thought we had a lot more great looks so, yeah, they have two grade As in the first so they took advantage of their opportunities, we had four or five and kept with it. A solid game through and through."
Harley gave Dallas a 1-0 lead at 6:27 of the first period on a shot from the high slot through traffic.
"We're not generating enough offense, but I thought defensively we were pretty good. We didn't shoot ourselves in the foot like we did last game (3-2 shootout loss to the Tampa Bay Lightning on Thursday)," Dallas forward Matt Duchene said. "I thought there were some steps in the right direction. When you go through a little bit of a gulley, you're not going to come straight out of it. You've got to work your way out of it. Big win."