Barmes hit his 20th home run of the season in the fifth inning, the third game in a row in which he's gone deep, a two-out solo shot to left field that made the score 4-1. He also continued to shine on defense, making the final two outs of the night in the field to preserve the win.
"I wouldn't know where to start, to tell you what a special player he is and has been to our club," Rockies manager Jim Tracy said of Barmes.
"It was nice to finally get my hands inside the ball and get the barrel to it, because I felt like tonight they were throwing me inside a lot," said Barmes, who also had a double in addition to popping out twice. "It was nice to get hold of one, and it turned out to be a big run for us."
In the Rockies' two wins over the Nationals over the past two nights, the club has hit five homers -- all solo shots.
"You'd like to see one of those every once in a while with the bases loaded," said Tracy, "but I won't beg."
The long-ball heroics helped starting pitcher Jason Marquis (14-8) move into a tie with St. Louis' Adam Wainwright for the most wins in the National League. Marquis allowed three runs on nine hits in six-plus innings of work.
"Marquis did a very solid job for us," Tracy said. "[He was] another starter who pitched us into the game to where we could start using our bullpen in situations that made sense."
When Marquis left with one on and no outs in the seventh, the triumvirate of relievers -- Franklin Morales, Rafael Betancourt and closer Huston Street -- continued to shine, combining for three innings of one-hit ball, the one blemish being a leadoff homer in the ninth off Street by Nationals catcher Josh Bard. After that, he retired the next three batters on groundouts for his 31st save of the season and converted his 23rd in a row, the longest such streak in the NL this season.
But the win didn't come easy and Tracy may have come away with just a few gray hairs.
The Rockies, who maintained their lead in the NL Wild Card race with the win, knocked Nationals starter Collin Balester (1-3) out of the game in the second inning, but could not quite put the game away as they left the bases loaded in each of the first two innings.
Balester had control issues from the get-go, walking the first three batters of the game to load the bases with no outs. Shortstop Troy Tulowitzki then laced a two-run double to left field to score Gonzalez and Dexter Fowler, and the fourth walk of the inning, to Brad Hawpe, reloaded the bases once again with no outs.
But Balester regrouped long enough to retire the side with no more damage on a pair of fly balls and a strikeout, giving the Rockies an early 2-0 lead that could have been much more lopsided.
The Nats rebounded quickly for a run in their half of the first as explosive leadoff hitter Nyjer Morgan led things off with a single, stole his 40th base of the season and scored on a triple by Ryan Zimmerman.
In the second, Balester was not much more effective, allowing a leadoff double to Marquis and an RBI triple to Fowler. After a walk to Todd Helton, Balester's fifth of the night, reliever Saul Rivera came on and stopped the bleeding. The Rockies once again left the bases loaded and only eked out that lone run to give them a 3-1 lead.
"We did not do a good job tonight from the standpoint of our situational hitting," Tracy said. "We left the first battalion stranded out there on the bases. We had their starter on the ropes big time, and then their bullpen settled in and did a very nice job and kept them in the game right there."
Washington, which has been playing over .500 ball since the All-Star break, scored two more runs in the fifth to keep the game close all night.
The Rockies collected nine hits on the night, and while only Gonzalez and Barmes tallied multihit games, with two apiece, veteran first baseman Helton drew four walks, falling one short of his own club record of five in one game.