Prior to the costly error, Jackson was dominant, allowing just one hit through the first five innings and he set down seven in a row between the first and third frames.
The only other run he allowed was in the sixth. Jackson gave up a one-out double to Omar Infante, who then advanced to third on a throwing error by Rick Ankiel in center field.
With Infante on third and one out, Jackson decided not to pitch around Stanton, who has been one of the hottest hitters in the league this month. That decision, too, proved to be costly, when Stanton took advantage of a fastball that missed its intended location and wound up over the middle of the plate. Stanton lined the offering down the left-field line for his 10th double of the month to knot the score at 1.
"It's just one of those things, it's a game of inches," Jackson said. "You get it in a little more and maybe he still gets a hit, maybe he doesn't. Who knows?"
Despite the hot start, Jackson finished the night after 6 2/3 innings and took the loss after giving up five hits and two runs -- one earned.
"Heck of a ballgame," Nats manager Davey Johnson said of Jackson's outing. "You can't do much better than he did."
Unless you're Marlins righty Anibal Sanchez, who was dealing on the mound, and was similarly dominant early, much like he has been throughout his career against Washington.
Through the first four innings, Sanchez held the Nats to no hits and just one baserunner -- a full-count walk to Carlos Maldonado with one out in the third. The Nationals finally got to him in the fifth, when Ian Desmond singled to the left side for Washington's first hit. Desmond stole second and then advanced to third on a John Buck error. Corey Brown, making his first career start, picked up his first RBI in the big leagues with a perfectly executed squeeze bunt to plate Desmond.
Getting RBI No. 1 out of the way was a relief for Brown. Doing so on a squeeze play was too, he said, especially considering it was the first time he can remember ever being asked to squeeze bunt.
Washington again threatened against Sanchez in the sixth, when Bryce Harper hit his fourth triple in 29 games. Sanchez was able to pitch around the three-bagger en route to a seven-inning start that improved him to 8-0 with a 1.97 ERA in 19 career starts against the Nats.
"I try to pitch like it's every day. I try not to think if Washington is coming or I'm going to Washington and I've got to win," Sanchez said. "I don't know who [it helps more], them or me. I know the record is good against that team. But I treat them like any other team. I try to throw strikes, keep the score down and win."
The Nationals had an opportunity to rally in the eighth, loading the bases with one out, but Miami reliever Steve Cishek struck out Harper before Ryan Zimmerman grounded into a fielder's choice to end the threat.
"We had them in a spot where we should've scored a run," Johnson said. "We had the right guys up, it just didn't happen. It's frustrating, but it's baseball."
Hanley Ramirez added a solo homer to lead off the bottom of the frame to seal the game for Miami, which set a new franchise record for wins in a month with 20, and Washington saw its lead in the National League East dwindle to 1 1/2 games, with 14 of the team's next 32 games coming against division foes.
"This is one of the better divisions in baseball, if not the best," Desmond said. "It's going to be fun; it's going to be a fun year."