Jackson (5-4) has now allowed 17 earned runs in 16 first innings this year, a 9.56 first-inning ERA. In innings 2-9, his ERA is 2.24.
"After you give up runs in the first inning, it's just a matter of coming and battling and keeping the game close," Jackson said. "Pretty much, it was a subpar performance backed up by a great offense and great defense."
Giants lefty Madison Bumgarner cruised through the first two innings, but the Nats' offense came to life in the third. With two outs, Danny Espinosa and Bryce Harper each singled before Zimmerman scored Espinosa with a double off the left-field wall. After Morse walked, Desmond worked a 2-2 count before ripping a single to center, scoring Harper and Zimmerman to tie the game at 3.
Since receiving a cortisone injection for his ailing right shoulder on June 24, Zimmerman is 17-for-46 (.370) with 16 RBIs. His two-run homer in the fifth inning was the fourth in that span and his seventh of the season. It also continued Zimmerman's hot hitting on Independence Day in his career. He is 10-for-20 (.500) with four home runs, 13 RBIs, five walks and eight runs scored on July 4.
"I was playing banged up for a while there," Zimmerman said. "When you try and play through things sometimes, it doesn't allow you to do the things you've been doing -- and that leads to other things."
Four pitches after Zimmerman's homer, Morse followed with his own shot to right field. After missing the first two months of the season with a strained right lat muscle, Morse is batting .288 with four homers and 16 RBIs.
Between Jhonatan Solano's homer earlier in the fourth inning and the back-to-back dingers from Zimmerman and Morse, the Nats went yard three times in six at-bats. Solano enjoyed the third multi-hit game of his first season in the big leagues, going 2-for-4 with two RBIs. In 24 at-bats, Solano is hitting .393 -- an added offensive bonus considering his principal responsibility is providing occasional rest for Jesus Flores.
"Baseball's a funny game," Morse said. "You really never get a lot of opportunities to have everybody hitting. That's just how it is. Some guys get hot, some guys don't. But when everybody gets hot and everybody's seeing the ball good, it's pretty fun."
Once Jackson escaped the first inning, he faced only one batter above the minimum in innings 2-5. After giving up eight runs in only three innings in his last start on June 28 at Colorado, both Jackson's resiliency and renewed velocity were welcomed signs for Nationals manager Davey Johnson.
"That was more like Edwin," Johnson said. "He had a much better fastball than the last two times out."
For the Giants, though, the hole dug by Bumgarner's poor start proved too much to overcome. He fell to 10-5 after allowing seven runs on nine hits over five-plus innings.
"You have to give [the Nationals] a lot of credit, they put a lot of good swings on balls," Bumgarner said. "It seemed like I made pretty decent pitches to get to two strikes and then leave the ball up or over the plate for something to hit. I had a hard time finishing guys."
In the sixth, the Giants cut the Nats' lead to 7-4 on a two-out double by Giants third baseman Pablo Sandoval. Sandoval supplied the majority of San Francisco's offense, going 3-for-4 with three RBIs. Jackson was pulled after the at-bat for left-hander Tom Gorzelanny, who pitched 1 1/3 innings before giving way to Sean Burnett in the eighth and Mike Gonzalez in the ninth.
In total, the Nationals' bullpen pitched 3 1/3 innings of two-hit, scoreless relief, lowering the staff's Major League-best runs-scored-per-game average to 3.47.
"That was, to me, the key to setting up the ballgame -- getting to Burnett and company," Johnson said.
The Nats' final offense of the day came in the eighth inning, on a two-run blast by Rick Ankiel. Gonzalez allowed a two-out single before getting Angel Pagan to ground out to third to end the game.
"I think I like this bullpen as good as any I've ever had," Johnson said. "I think the depth in this bullpen and the versatility of this bullpen for different lineups is the best I've ever had."