The Nats, in turn, have put seven on against Chicago starter Dylan Axelrod, who has already thrown 74 pitches.
Still, it's just a 3-1 ballgame, with the Nats holding the lead as we go to the fourth.
The two teams have combined to strand nine runners and have gone 2-for-10 with runners in scoring position.
Haren has given up three doubles already tonight, one in each inning, but he's managed to dance his way out of trouble.
The right-hander struck out Axelrod with a runner in scoring position to end the second and left the bases loaded in the third by getting Alexei Ramirez on strikes to end the inning.
Haren has five strikeouts already and has shown great movement on his splitter and two-seam fastball. We'll see if he can limit the extra-base hits the rest of the way out.
Meanwhile, the Nats have really worked Axelrod over thus far tonight. It's not often you see a bullpen stirring in the third inning when a pitcher has allowed just two runs to that point.
Axelrod needed a whopping 40 pitches to get through the first inning, despite facing just six hitters. Jayson Werth worked a 10-pitch at-bat, singling to left, and Adam LaRoche brought Werth in with an RBI single on the seventh pitch of his at-bat.
Bryce Harper and Ian Desmond added RBIs in the third to give the Nats their 3-1 lead.
Update: Haren gave up two more runs in the top of the fourth, tying the game, 3-3.
The right-hander got a bit of bad luck in the fourth, as Conor Gillaspie's bloop to shallow center dropped between Desmond and center fielder Denard Span, and then Axelrod's popped-up bunt scooted past a diving LaRoche to go for a single.
Had Axelrod been retired, it would've been a runner at second with two outs. Instead, there were two on with one out, and back-to-back RBI singles by Alejandro De Aza and Jeff Keppinger have tied the game.
Haren's at 84 pitches through four. Zach Duke had been warming when Haren got into trouble, but he's since sat back down.