Kurt Suzuki gave the Nationals the lead in the bottom of the second and then made a tremendous play a half-inning later to ensure the Cubs didn't grab the lead right back.
Up with two on and two outs in the second, Suzuki smoked a Jeff Samardzija fastball off the right-center field wall. Ian Desmond and Danny Espinosa both came around to score, giving the Nationals a 2-1 lead over the Cubs.
This marks Suzuki's first two-RBI game since April 17.
The Cubs came right back with back-to-back doubles leading off the top of the third inning, tying the game. Samardzija helped his own cause, ripping a ball into the corner in left, and then he came around easily on Starlin Castro's double to right-center.
Castro then tried to score two batter later when Anthony Rizzo ripped a single to right, but Roger Bernadina cut him down with his 22nd career outfield assist.
Bernadina's throw was decent, but Suzuki's effort behind the plate made the out at the plate possible.
The throw from Bernadina was to the first base side of home plate, forcing Suzuki to make the catch and then lunge all the way across the plate to try and apply the tag on the speedy Castro.
Suzuki laid out and slapped the tag on Castro just before he got to the dish, and home plate umpire Angel Hernandez correctly called Castro out.
It's a 2-2 game midway through the fourth. Ross Detwiler hasn't been at his sharpest tonight, but he's gotten some strong defensive plays from Suzuki, Bernadina, Danny Espinosa and Adam LaRoche and has allowed two runs through four.
Hernandez, by the way, was booed by the crowd here at Nats Park when he was introduced just before first pitch. He was the ump who blew the call a couple nights ago in Cleveland, when replays clearly showed a ball going over the wall in left field and then bouncing back into play.
With Hernandez at the helm, that umpiring crew ruled the play a double even after looking at replays, costing the Athletics the game-tying run in the ninth inning.
Update: Desmond crushed a line drive two-run homer to left in the fourth, giving the Nats a 4-2 lead.
It's Desmond's fifth homer of the season and also gave him his 500th career hit.
The top four hitters in the Nats' order tonight are 1-for-8 with three strikeouts. The Nats' 5-8 hitters are a combined 4-for-8 with four RBIs.
Update II: A three-run fifth inning has allowed the Nats to open up a nice cushion over the Cubs and given them a 7-2 lead.
Desmond is now 3-for-3 with three RBIs after his double to right in the fifth that plated Ryan Zimmerman. Should Desmond notch a triple at some point later tonight, he'll have himself a cycle.
Espinosa followed Desmond's double with one of his own, a shot to right-center that bounced off the wall. Two more runs came around, giving the Nats a five-run lead.
LaRoche doesn't have a homer since April 20, but he is now 10-for-17 over his last six games and has reached base 15 times.