Harden (6-6) gave up three hits over six innings for the win. He fanned seven, including career strikeout No. 700 when he got Adam Dunn looking at strike three to end the fourth. The right-hander now has 702 Ks over 124 career games.
"After the break, it's nice to have a couple days off and regroup," Harden said. "It helps put some things behind you and put the first half behind you. There's a lot of games left, and it's almost like you're starting over. Tonight, hopefully, set the pace for the second half of the season."
Harden is now 4-1 with a 2.17 ERA away from Wrigley Field. Expect to see him in the road grays more as the season winds to a close.
"I don't see anything statistically," he said. "I haven't really thought about it too much. I've had some tough games at home with the wind blowing out and the ball carrying."
"I think there's reasons for it," Piniella said.
One theory is that day games seem to wear out Harden more than night games, when the weather is cooler. He's had some problems with mechanics, with his arm dragging and his body opening up. Hitters can see the ball easier if he does that, and his changeup flattens out. He can't be effective that way.
On Thursday he was able to follow through on his pitches and get more ground balls, and he got the job done. It's something he hopes to continue to do.
"Our starting pitching has been great," Harden said. "I think it's the key to the game, and it's tough if you're hot and cold and hot and cold. Something I want to do in the second half is be consistent with my starts. Tonight I really felt great with some of the stuff I've been working on. I'm feeling the difference, and now I have to go out in my next start and do it."
"We were kind of hoping to stay close and eventually get his pitch count up to where he was out of the game and we would do something against their bullpen," said Nationals manager Jim Riggleman, "but their bullpen guys came in and did a good job, too."
The loss spoiled Riggleman's return as a skipper. He took the place of the dismissed Manny Acta at the All-Star break for the Nationals, who have the worst record in baseball at 26-62.
"First of all, you don't like to see anybody get [dismissed]," Piniella said. "Riggleman has managed in Chicago, he's managed in Seattle. Sometimes it takes a while."
The Cubs took advantage of miscues by the Nationals. Koyie Hill reached on a throwing error by third baseman Ryan Zimmerman to lead off the third, and two outs later, he scored on Ryan Theriot's double.
Lee made it 2-0 when he crushed a 3-2 pitch from John Lannan (6-7) to right for his 18th homer. It was his fifth away from Wrigley Field and second off a left-hander. Lee entered the game batting .301 at home and .254 on the road.
"Derrek basically, for the past month or so, has carried us offensively," Piniella said. "When he hits, we put runs on the board. What we need now is for everybody to start chipping in."
Lee had 15 home runs at the All-Star break a year ago and just five in the second half of 2008.
"It's one game," Lee said, "but I didn't have good second-half power or hitting [last season]. Last year I fell out of rhythm. I'm going to try to be a little more consistent this year."
Washington's Nyjer Morgan reached safely on a bunt single to lead off the sixth, stole second and reached third on Hill's throwing error before scoring on Nick Johnson's groundout.
Reed Johnson added a two-out RBI single in the Chicago seventh, and the Cubs added three in the ninth on an RBI single by Hill, an error and a sacrifice fly.
"The All-Star break is always a nice time to refresh and regroup," Lee said. "I felt a lot better than I did after that doubleheader on Sunday. The three days really helped."
Piniella, who had an eventful day, meeting President Barack Obama at the White House, began the season's second act without his regular catcher (Geovany Soto) and one of the starting pitchers (Ryan Dempster). The team has stayed within reach of a three-peat in the National League Central despite losing others to injury, the most significant being Aramis Ramirez, who was out for two months because of a dislocated shoulder.
The Cubs are ranked 15th in runs scored in the NL, and they need Ramirez, Alfonso Soriano and Milton Bradley to get back on track.
"I know there's some 'ifs,' but they're all very possible 'ifs,' " Piniella said. "You've got to do it on the field."