Jackson is also piling up the strikeouts. The righty has 29 over his last three games, and 139 overall, which ranks third on the team. Jackson downplayed his strikeouts.
"It's just a matter of throwing strikes," Jackson said. "I really don't pitch to strikeouts. I really don't know how many strikeouts I have until someone tells me after the game. I just pitch and try to go as deep in the game as can.
"I try not to get caught up in strikeouts, because it takes away from pitching. If there is a situation where I need a strikeout, I will definitely go for it. But other than that, I pitch to contact."
St. Louis was only able to get runners in scoring position twice in the game -- in the fifth and eighth innings.
In the fifth, the Cardinals had a runner on second with two outs when Skip Schumaker singled to put runners on first and third. But Rafael Furcal popped up to shortstop Ian Desmond to end the threat.
In the eighth inning, an error by Ryan Zimmerman allowed Bryan Anderson to score the Cardinals' only run.
"Jackson threw the ball well," Cardinals manager Mike Matheny said. "We chased a lot of balls out of the zone. He executed his pitches and we got away from getting him in the zone. Good things can't happen when it goes like that."
Jackson felt he didn't have an advantage over the Cardinals just because he played with them last year.
"Just as well as I know them, they know me," Jackson said. "Like I always said, it was a matter of executing. The run support I received tonight, it helps. You want to go out and secure the lead.
"It's a lot of fun. They are trying to hit me as I'm trying to get them out. They were definitely not friends while the game was going on, but it's a lot of fun to come out and throw against the guys I had a chance to battle with and win a ring."
The Nationals were able to give Jackson run support in the opening inning. After Jayson Werth reached base on a walk, Bryce Harper hit a two-run homer off left-hander Jamie Garcia. It was Harper's 15th homer of the season and third in the last two games. Tony Conigliaro, Mel Ott, Ken Griffey Jr. are the only teenagers to reach 15 homers in a season.
"It felt pretty good," Harper said. "I think having Werth hit in front of me just gets me going and he sets the tone. It just calms me down and he lets me go up there and just swing it."
Werth scored his second run of the game in the third inning. With the bases loaded and one out, Adam LaRoche drove him in with a sacrifice fly to right field.
Two innings later, Werth added to the scoring by hitting a solo home run over the left-field wall to make it a 4-0 game. Werth ended up going 2-for-4 with three runs. Since coming off disabled list on Aug. 2, Werth is 31-for-92 [.337] with a home run and 10 RBIs.
"I've been swinging the bat well. I haven't hit any balls that went over the fence, but it was nice to do that," Werth said. "It's a lot easier when you don't have to sprint around the bases. Hopefully, there will be more to come."
In the sixth, the Nationals added two more runs, which were charged to Garcia. With the bases loaded and right-hander Fernando Salas on the mound, Werth grounded into a fielder's choice, but Danny Espinosa scored on the play. Harper then singled to left-center field to drive in Jesus Flores.
Flores then drove in two more runs in the next inning when he singled to left field off Lance Lynn.
"We've run into a bit of a bad spell," Cardinals outfielder Matt Holliday said. "Then they are swinging the bats well, and combine that with Edwin pitching well tonight, that's a bad formula."
The Nationals have now won back-to-back games, improved their record to 79-51 and increased their lead in the National League East to 5 1/2 games over the Braves.
"We play the Cardinals. We have to take it one game at a time," Jackson said. "We can't look too far ahead. We can't afford to do that. We have to play each series and take one game at a time."