"I think we just got them off the rush, got them scrambling a little bit," Daley said. "You get pucks to the net and pick up rebounds, it's going to lead to scoring chances. [Ray Whitney] was just behind the net and gave me a nice pass in front."
Dallas gained some breathing room with an insurance goal from captain Jamie Benn at 6:58.
"I just thought [Lehtonen] looked to me like he was locked in," Stars coach Lindy Ruff. "He was focused. He didn't pay a lot of attention to a couple of bumps. The desperation time now is people go to the net hard and there's going to be people falling into you and people taking you out, but it's going to be his job to battle through that."
Lehtonen won for the first time since beating the Vancouver Canucks on March 6. He missed four games with a concussion sustained March 8 against the Minnesota Wild before returning Tuesday at the Pittsburgh Penguins, a game the Stars lost 5-1.
"It's been a while (since my last win)," Lehtonen said. "It was nice to play at home."
The victory, combined with the Phoenix Coyotes' 4-2 loss to the Boston Bruins, moved the Stars (33-26-11) within two points of the second Western Conference wild-card berth in the Stanley Cup Playoffs.
In the past eight days, the Stars lost to the Calgary Flames in a shootout and three times on a road trip against the Winnipeg Jets, Penguins and Philadelphia Flyers.
Ottawa, winless in six straight, scored first when Erik Karlsson's one-timer from the high slot went under Lehtonen's glove 3:27 into the game. Senators center Colin Greening collected a free puck inside the Dallas zone and raced up the right side before feeding Karlsson from the right circle. The puck was free because Dallas defenseman Aaron Rome missed it while it was coming around the end boards behind his own net.
The Stars outshot the Senators 14-7 in the first period, 31-19 through two, and 44-27 for the game.
"I didn't think we defended or played terribly, but at the end of the day, we didn't play hard enough and we didn't play long enough to find a way to win the game," Senators coach Paul MacLean said.
Dallas had two opportunities eight minutes into the second period. The first, a wrist shot by defenseman Alex Goligoski, was turned away by Lehner with a pad save. Jamie Benn then misfired on a backhand on the rebound.
Kyle Turris had a great chance to put the Senators ahead by two goals on a breakaway at 8:10 of the second period, but his wrist shot hit the right post.
"It's frustrating," Turris said. "It's very frustrating and we've got to figure it out."
Dallas tied it late in the second when Cody Eakin tapped in a free puck for his 14th goal of the season during a 4-on-4. Lehner turned aside the initial shot by Stars rookie Valeri Nichushkin with a pad save. Eakin saw the puck lying under Lehner and slipped it in with 4:53 to go.
"We've been on the losing side for a few games last week. This was an opportunity," Eakin said.
That game-tying goal epitomized how badly things have been going for the Senators.
"Yeah, I don't think the first goal was a goal, but you know what, we're not going to get the post-and-outs, and everything goes post-and-in for us right now," Lehner said. "It's tough for all of us."
The Senators lost right wing Bobby Ryan to a lower-body injury with 7:28 remaining after Ryan went hard into the boards behind the Dallas net. Ryan led with his right hip and had to be helped off the ice by Turris.
"We're not sure," MacLean said of Ryan's status. "It's kind of up in the air. It's not something that's definite. It's just a reaggravation of something. We'll see how it is tomorrow."
Dallas was playing without veteran wing Erik Cole, who missed his first game since March 10, 2010, when he was with the Carolina Hurricanes. Cole, who is sidelined with an upper-body injury, skated in 296 consecutive games prior to his absence.
"[He's] day-to-day," Ruff said. "Just suffered a little bit of a minor injury in the game, and we didn't know really till this morning whether he'd be able to go and wasn't able to. So we'll get some further tests on him [Sunday]. Kind of the same thing he was hampered with early in the year."
The Stars received a lift from the return of veteran center Shawn Horcoff, who missed the past four games with a broken finger. Horcoff skated on the left side of Dallas' fourth line alongside center Chris Mueller and right wing Alex Chiasson, who had been a game-time decision after leaving practice early Friday.
"I thought [Horcoff] played well. I thought he skated well," Ruff said. "They gave us some good shifts early, probably our better line early in the game. I thought Shawn did a nice job for us."