In what's become a one-sided series between the NL Central's two top teams, Chicago (64-44) continued its dominance with a 7-2 win Wednesday to move four games ahead of Milwaukee.

"Games in your own division with teams that are right behind you; (you) come in here one game up, it could have easily turned around and been the other way," Wednesday's winning pitcher Ryan Dempster said. "We knew we had to play good baseball."

The Cubs have outscored the Brewers 20-7 and look for their first four-game sweep in Milwaukee since May 12-15, 2003.

The Brewers (60-48), meanwhile, have lost a season-high four straight and are in a virtual tie with St. Louis for second in the division and the wild card lead.

After being held to one total run by Chicago's Carlos Zambrano and Dempster the last two days, Milwaukee - 0-for-15 with runners in scoring position in this set - won't have it easy against Harden.

"You can talk about it all you want with runners in scoring position," Milwaukee manager Ned Yost said. "That stuff happens when you face All-Star pitchers."

Harden (0-1, 1.04 ERA) has allowed two earned runs and eight hits in 17 1-3 innings over three starts since being traded to Chicago from Oakland on July 8. He's struck out 10 in each contest, and gave up a run and two hits in five innings of a 3-2, 12-inning loss to Florida on Saturday.

"The guy doesn't give up any runs and doesn't get a win," Chicago first baseman Derrek Lee said. "You feel a little bad for him. But I have a feeling he's going to be good the rest of the way and we'll get him a few wins."

Harden, who is making is first appearance against Milwaukee, could be in good shape if the Cubs continue to hit like they have this week.

On Wednesday, Alfonso Soriano, Ryan Theriot and Reed Johnson each had three hits for Chicago, which has won four in a row overall and on the road.

Theriot, whose two-run triple highlighted a three-run sixth inning, is 6-for-13 with two triples in the series and batting .366 against Milwaukee this season.

Soriano, meanwhile, is 9-for-17 with seven runs scored and five RBIs in his last four games. He's also batting .333 (7-for-21) against Milwaukee's Thursday starter Dave Bush.

Bush (5-8, 4.51) makes his second start since the Brewers implemented their fifth-starter platoon system where he throws at home, while Seth McClung fills that spot on the road. Bush is 4-2 with a 2.85 ERA at Miller Park this season, compared to 1-6 with a 7.11 ERA in eight starts on the road.

"This is what we're going to do for a while, so I have to figure out a way to stay a little sharper," Bush told the Brewers' official Web site.

He allowed four runs and nine hits in five innings, but didn't factor in the decision of Milwaukee's 6-4 win over Houston on Saturday.

The right-hander has struggled no matter where he's faced the Cubs, going 1-6 with a 4.88 ERA. He allowed six runs in 5 1-3 innings of a 6-3 loss at Chicago on April 3 for his fourth consecutive defeat to the Cubs.