Edwin Jackson received the run support to pick up his second win of the season. (Jonathan Newton/The Washington Post)

The void in the middle of their lineup both raised concerns and allowed the Washington Nationals to ponder what may be possible. Adam LaRoche carried them in April and vanished in mid-May. Ryan Zimmerman played like an imposter both before and after he spent two weeks on the disabled list. Michael Morse was a phantom for 50 games. And still Washington entered Wednesday night in first place in the National League East.

“When Michael Morse starts hitting and these guys start doing things they’re capable of doing,” Manager Davey Johnson said, “we’re going to be hard to beat.”

In their 5-3 victory over the New York Mets at Nationals Park, the middle of the Nationals’ order came alive and offered a glimpse of what their offense may be capable of if Zimmerman, LaRoche and Morse all find their swing at the same time. The Nationals’ 3-4-5 hitters have been equal parts inconsistent and nonexistent, but Wednesday they went 5 for 9 with two walks and drove in all five of the Nationals’ runs.

“This is what we were talking about in spring training,” LaRoche said. “This is what we’re capable of doing. It’s just getting everybody going at once.”

LaRoche provided the most crucial effort, launching a three-run homer in the first inning off Mets rookie starter Jeremy Hefner and driving in four runs. By himself, LaRoche gave Edwin Jackson all the runs he required for his second win of the season.

The Nationals’ top three starting pitchers overshadow Jackson, but Wednesday he lowered his ERA to 3.11 while yielding two earned runs in seven innings on three hits and four walks, giving a needed break to the bullpen, every member of which pitched Tuesday night.

“After having a game like we had last night, I had the incentive to try to help those guys out,” Jackson said. “They’ve been helping us all year.”

By the time “Ready Or Not” blared and Tyler Clippard jogged in from right field, the Miami Marlins had already lost to the Atlanta Braves. Clippard’s fifth save in five tries increased the Nationals’ lead to two games. The Nationals are 14-7 against the NL East, perhaps the toughest division in baseball.

The middle of the Nationals’ order made their statement, but the 19-year-old who drilled a walk-off hit the night before sparked their pivotal rally. With one out in the first, Bryce Harper ripped a groundball toward second baseman Daniel Murphy. The ball deflected off his glove, and without a moment’s hesitation Harper bolted for second.

Zimmerman worked a walk, which brought LaRoche to the plate. LaRoche had fallen into an 11-for-70 funk, including 0 for 13 on this homestand. His on-base percentage dropped from .431 on May 12 to .360 entering Wednesday night.

LaRoche rarely takes early batting practice, but he senses when he needs it. Tuesday , he joined a small cluster of teammates at 2:30 p.m. and took extra pitches.

“It’s a funny feeling as a hitter,” LaRoche said. “I don’t know if I can explain it. When you’re seeing the ball big, everything’s quiet. You’re not in a hurry to get through the at-bat. That’s kind of what I’ve been hunting the past few days. I have no idea how to describe it. I honestly a lot of times don’t know where to find it.”

As Hefner took his sign, Johnson turned to bench coach Randy Knorr in the dugout. “He’s been quiet for a long time,” Johnson told him. “He’s going to start getting hot.”

Hefner threw a hanging curveball on the inside half of the plate — “on a tee for him,” Hefner said. LaRoche was not looking for a curveball. He gets in trouble when he starts guessing pitches, and he had resolved to see the ball and adjust.

Hefner’s curve looked like a beach ball, and LaRoche smashed it. The ball soared high into the twilight toward right field, and it landed five rows deep behind the curly W logo on the right field wall.

“It’s a whole new ballgame,” Johnson said. “There’s not going to be much let-up in the middle of that lineup. The first two guys are going to get on, and then the thunder’s coming. I’ve been waiting on it.”

The Nationals were poised to send Hefner to an early shower. But he settled in, and the Nationals’ lead dwindled to a run by the fifth, when the middle of the lineup came up to bat with two outs. Zimmerman kept the inning alive with a single to right field. LaRoche smoked a line drive up the middle, through the Mets’ infield shift, to put two on base for Morse.

Morse may have played Saturday and Sunday, but the Nationals (32-22) didn’t really have him back from his strained lat muscle until this series against New York (31-26). He went hitless in his first nine at-bats of the season. He was out in front, Johnson said, a typical sign of anxiousness for a player coming off a long layoff.

Finally, Morse said, “it kind of clicked a little bit.” In both of his at-bats Tuesday, Morse crushed doubles to right-center, the kind of hit on which he built his breakout 2011 season.

He carried the feeling over into Wednesday. In the first inning, he belted a single into right field. Then, with two on and two outs in the fifth, he smoked a 1-2 sinker down the right field line, a rocket that skipped over first baseman Ike Davis. Zimmerman raced home to put the Nationals ahead, 4-2.

“That’s where I want to stay,” Morse said. “I’m feeling good. I’m seeing the ball a lot better.”

LaRoche would add one more blow, a sacrifice fly to center field in the seventh. He had found the feeling he was hunting for. The Nationals, for one night, had filled the void in their lineup and viewed what they are capable of.