Washington’s first sweep at Turner Field in three years left the Braves with a seven-game losing streak, their worst skid since dropping nine in a row in 2010.
The Nationals took the lead with four runs in the sixth. They scored at least seven runs in each game of the series.
At 29-18, the Nationals moved 11 games over .500 for the first time since their 2005 inaugural season in Washington.
Gonzalez (7-1) struck out 10 and outpitched Brandon Beachy (5-3) in the matchup of ERA leaders.
Gonzalez gave up two runs and three walks in seven innings. Craig Stammen allowed two hits in 1⅔ innings before Sean Burnett recorded the final out.
Beachy’s 1.77 ERA, the best in the major leagues, did not change as he permitted three runs – only one earned – in five-plus innings. He was pulled with the game tied at 2 after hitting Danny Espinosa with a pitch to open the sixth.
The Nationals jumped on former Washington pitcher Livan Hernandez following Beachy’s exit. Hernandez walked Rick Ankiel on four pitches before Jesus Flores gave Washington the lead with an RBI single. Steve Lombardozzi added a two-run double.
The losing streak is having a toll on Braves fans, who booed after the hit by Lombardozzi. There were more boos from the crowd of 38,543 after Lombardozzi scored easily from second when right fielder Jason Heyward bobbled Ryan Zimmerman’s single.
Flores had three hits. He left the game following his third hit in the seventh.
Harper hit his fourth homer, a high shot into the right-field seats, off Hernandez in the eighth.
The Braves scored a run without a hit in the first. Michael Bourn walked, stole second, moved to third on Tyler Pastornicky’s sacrifice and scored on Martin Prado’s groundout.
Atlanta added a run in the third. Bourn had a one-out triple for Atlanta’s lone hit off Gonzalez and scored on Pastornicky’s suicide squeeze.
Washington scored two unearned runs in the fourth. The Nationals loaded the bases on walks to Adam LaRoche and Espinosa and a throwing error by Pastornicky on Ian Desmond’s grounder to shortstop. Flores drove in LaRoche with a single, and Gonzalez hit a sacrifice fly.
Pastornicky had another error in the seventh when he bobbled a grounder by Ankiel.
The Braves, who put third baseman Chipper Jones on the 15-day disabled list on Saturday with a left leg contusion, remained short-handed. First baseman Freddie Freeman was held out with ongoing vision problems and catcher Brian McCann was still recovering from an illness.
Third baseman Juan Francisco did not start after manager Fredi Gonzalez said he “tweaked something” on Saturday, when he had three hits. Francisco had a pinch-hit single off Stammen in the eighth.
Washington’s only other sweep this season came in a weather-shortened series. The Nationals won two games against Miami on April 20-21 before the third game was postponed due to rain.
NOTES: The Nationals had been 0-9 this season when closing out a series with a sweep on the line. ... Plate umpire Kerwin Danley went down to the ground in the third inning after he was hit in the groin area when a pitch from Beachy bounced past C J.C. Boscan. Danley remained in the game following a visit from Braves assistant trainer Jim Lovell. ... The last time the Nationals were 11 games over .500 was July 25, 2005, when they were 55-44. ... The Braves will open a three-game home series against St. Louis on Monday with RHP Tommy Hanson facing RHP Lance Lynn. The Nationals open a series at Miami on Monday. RHP Jordan Zimmerman will face RHP Carlos Zambrano.