"We had just enough offense to win," Baker said after his 3,000th game as a big league manager. "That was a big double by Hanigan. Just a big victory for us, back to 30 over and one step closer."
The Reds (89-59) have a magic number of four to clinch the division championship over St. Louis. The Cardinals beat Houston 4-1 on Tuesday night.
Bailey (12-9) took a two-hit shutout into the eighth before Darwin Barney had his second single of the night and pinch-hitter Bryan LaHair hit an RBI double to make it 3-1. Sean Marshall then came in and hit pinch-hitter Dave Sappelt before getting a strikeout and grounder to end the threat.
Jonathan Broxton worked a perfect ninth for his third save in five chances with Cincinnati, which acquired him in a July 31 deal with Kansas City. The big right-hander has recorded 11 consecutive scoreless appearances, allowing just five hits and converting each of his three save opportunities during the streak.
Bailey allowed four hits, struck out four and walked two while improving to 2-0 with a 1.55 ERA in four starts this month. He is 3-0 against the Cubs this season and 5-2 for his career.
"Once we scored those three runs, I really put a lot of effort into putting up some zeroes," Bailey said. "Really wish I could have finished that eighth. I threw a pretty good pitch, LaHair just went down there and got it. Nothing you can really do about that."
Cubs starter Justin Germano was working on a shutout before he was pulled after he walked the first three batters in the sixth -- Joey Votto, Ryan Ludwick and Jay Bruce. Manny Corpas came in and Hanigan hit a drive to right-center with one out that cleared the bases.
"I had bases loaded, let it come to you in that situation. Just trying to put the ball in the outfield and fortunately it got over their heads," Hanigan said. "It worked out."
"You got three quality veteran hitters up there and after seeing him that was their third time, I think they kind of waited him (Germano) out," Cubs manager Dale Sveum said. "We got the out and just couldn't get the ball on the ground with Corpas. Hanigan obviously put a nice swing on the ball that changed the whole game around."
Germano (2-8) lost his sixth straight start. He gave up three hits, walked five, hit two batters and threw a wild pitch.
"I don't think I've ever walked the bases loaded before in my professional career, so that was a first and pretty much the worst time to ever do that," Germano said. "I was just missing and they were good takes on their part."
Baker said he had no special desire to clinch the division at Wrigley Field, where he managed the Cubs for four seasons, got them within five outs of the World Series in 2003 and was not brought back after the 2006 season. He said he just wanted to clinch as soon as possible and it doesn't matter where. ... Monday night's game between the Pirates and Cubs was delayed by storms for 3 hours, 37 minutes. The first pitch was thrown at 10:42 p.m. CDT and the game ended at 1:28 a.m. Tuesday night's game lasted 2 hours, 51 minutes. ... Sveum said 2B Darwin Barney, who has stretched his errorless streak to an NL-record 133 straight games, is a core player for the future because his defense is a game-changing skill. Barney also has a 13-game hitting streak ... Game 2 of the series on Wednesday night pits the Reds' Mike Leake (8-9) against Chris Rusin (1-2).