"You've just got to keep beating a team when it's down," Church said. "You're supposed to win these games."
New York scored four unearned runs off Daniel Cabrera to build an early cushion for Pelfrey, who missed his previous turn due to forearm tendinitis.
Mets manager Jerry Manuel, recently critical of his starting pitchers besides Johan Santana, said before the game that he was most concerned about seeing quality stuff and velocity from Pelfrey, rather than sharp command.
But the 6-foot-7 right-hander had his sinker working, generating 14 consecutive outs on grounders before Elijah Dukes' RBI triple chased him with two down in the sixth.
"I saw good stuff. I didn't see great stuff," Manuel said. "He's nasty right now, but he's not filthy."
Helped by solid glove work behind him, Pelfrey (2-0) allowed two runs, six hits and three walks while striking out one. Sean Green, Bobby Parnell and Brian Stokes followed with scoreless relief before 39,960 fans on a beautiful afternoon.
"I just felt like, a little dead. But I was able to make pitches when I had to and the guys behind me played great," Pelfrey said. "I think we need to get on a little streak. I think if you look at our losses so far, most of it's been because of starting pitching. We all know that. We're going to get this thing turned around and figured out."
One day after going 2-for-18 with runners in scoring position and stranding 13 during a 4-3 win, the Mets wasted plenty of early chances to break this one open, too. They finished 4-for-11 with RISP, improving their season average in those situations to .253.
"The last couple games we've been terrible -- pretty much the whole season," Church said. "Everybody knows that we're a good team. I think once it clicks, it's not going to stop."
The Nationals played poorly behind Cabrera (0-2), who lasted only 2 1/3 innings. They committed three costly errors while dropping to 0-8 on the road and 3-13 overall, the worst record in the majors.
With two outs in the first, Dukes misplayed David Wright's deep drive to center for an error that allowed two runs to score. Dukes had the ball lined up but appeared to lose it in the sun for a moment and completely whiffed when he opened his glove to try for the catch.
Church followed with an RBI single, making it 3-0.
"That first error I really think just took the air out of us," Nationals manager Manny Acta said. "I know it would make a good press conference, but I'm not going to throw things. At least not in front of you guys."
Beltran hustled for a run-scoring infield single in the second and the Mets added an easy run in the third when first baseman Nick Johnson made a throwing error on Pelfrey's bunt.
Another throwing error, this one by catcher Wil Nieves, permitted a run to score in the sixth. Church added a two-run single to make it 8-2.
"We're making mistakes that big league teams should not make," outfielder Adam Dunn said.
Dukes had an RBI single in the fourth, but Pelfrey got out of the inning with one of the two double-play grounders he induced.
- Mackenzie Brown, the 12-year-old girl who pitched a perfect game against boys for her New Jersey Little League team, threw out the first pitch and sat with her family behind home plate. She got to meet several Mets in the dugout before the game, including her favorite player, Wright, who gave her a bat.
- The Nationals have yielded 12 unearned runs in 16 games.