Spezza scored two goals and Martin Gerber stopped 28 shots for his second shutout, leading Ottawa to a 3-0 victory against Montreal on Thursday night.
Spezza, who was cut in the mouth by a high stick later in the game, scored on a power play in the first period. He hit the 30-goal mark for the second successive season with another goal in the middle frame.
Antoine Vermette also scored for the Senators, who won their third in a row to draw even with Montreal with 87 points.
Ottawa took over the division lead by virtue of their 40th victory, one more than the Canadiens. Both teams have 10 games remaining. The Senators, Canadiens and Pittsburgh Penguins trail East-leading New Jersey by one point.
"You don't want to put too much stock in one game but it was an important game for us," said Spezza, who had stitches on the left side of his mouth after he was high-sticked by Guillaume Latendresse in the third period.
"We were ready right from yesterday in practice, we were snapping it around pretty good. This morning we were pretty focused. From here on in they're pretty important games so we've got to get ourselves geared up. I thought we played like a good solid team and we played a playoff-type game."
Tempers flared with 1:17 remaining after Montreal's Andrei Kostitsyn checked Chris Kelly in the left corner behind the Senators net. Ottawa's Christoph Schubert got the only penalty on the play, a roughing minor after he grabbed Canadiens captain Saku Koivu from behind.
Gerber recorded his ninth career shutout, his first since he turned aside 35 shots in a 2-0 victory against the New York Rangers on Oct. 6 in Ottawa's third game of the season.
"We really played good from the start to the end," Gerber said. "We really had a big team effort."
Cory Stillman assisted on both of Spezza's goals.
Carey Price made 21 saves for Montreal, which has two games left with the Senators.
"The special teams obviously played a big role," Koivu said. "We didn't get our power play going the way we wanted and we didn't create those chances that we usually do. On the other hand, they scored two power-play goals and I thought that was the difference."
Ottawa has won five of six against the Canadiens this season, including a 6-1 home victory on Feb. 9 in which Spezza recorded his first NHL hat trick.
Senators captain Daniel Alfredsson assisted on Spezza's opening goal 8:21 in. He returned to the lineup after missing four games because of a back injury.
"I was pretty confident after the morning skate," Alfredsson said. "It went pretty good so it obviously was a lot of fun to get in there, especially getting a win."
Spezza was at the edge of the crease when he deflected Stillman's shot past Price.
The Senators' playmaking center made it 2-0 when he scored 27 seconds into the middle period on a play that required a video review.
Spezza was behind the goal line when he batted a puck out of the air and off Price into the net. Replay officials confirmed that Spezza's stick didn't make contact with the puck above the height of the crossbar.
"I knew it was a goal for sure because the only way I could score that was if my stick's below the crossbar because I kind of whacked it out of the air off his back," Spezza said.
Vermette added to Ottawa's lead with his 17th goal late in the second. The speedy left winger pounced on a rebound of Kelly's shot to beat Price.
- Spezza had a career-high 34 goals last season.
- Gerber shared a shutout with Ray Emery in a 6-0 victory at Carolina on Dec. 12. Gerber made 31 saves after taking over for Emery, who stopped the only shot he faced before leaving the game 5:24 into the first because of a hip injury.
- RW Brian McGrattan and LW Nick Foligno were healthy scratches for Ottawa.
- Canadiens C Steve Begin missed his eighth consecutive game because of a groin injury.
- D Patrice Brisebois, RW Mathieu Dandenault and C Mikhail Grabovski didn't play for Montreal.