The hosts can sweep the set by sending the Reds to their first six-game skid in three seasons Wednesday.
Jonathan Lucroy led off the ninth inning with his second homer of the game to give Milwaukee (56-45) a 4-3 victory Tuesday. The Brewers, who own a 1 1/2-game lead over St. Louis in the tight NL Central, lost 13 of 16 prior to taking the first two of the series.
"I'm glad to help the team out, contribute and get it done," said the All-Star, who was 5 for 42 in his previous 11 games.
Heading into the All-Star break, Cincinnati (51-49) averaged 5.3 runs while winning seven of the nine to trail the Brewers by 1 1/2 games. However, the Reds are in fourth place and 4 1/2 back after they've returned to hit .186 and score 11 runs in going 0-5 on a six-game trip.
Though it finished 2013 with five straight losses before dropping the NL wild-card game, Cincinnati hasn't lost six in a row in the regular season since May 18-23, 2011.
"We just haven't executed," manager Bryan Price said. "We haven't swung the bats well. We haven't gotten a quality start.
"And we haven't played particularly good defense, we've missed some signs and just haven't played terribly well."
Ryan Braun and Aramis Ramirez also homered for the Brewers, who have won three straight at home following a seven-game skid there.
Braun is batting .410 with two homers and eight RBIs during a 10-game overall hitting streak, and .426 with 13 RBIs while hitting safely in 13 straight at home.
Teammate Kyle Lohse (10-4, 3.16 ERA) is 0-1 with a 3.97 ERA in two starts against the Reds this season, but faces them at Miller Park for the first time since going 2-1 with a 1.99 ERA versus Cincinnati there in 2013.
The right-hander overcame a season-high 10 hits to yield just a run in seven innings of a 4-2 win at Washington on Friday.
"That's being able to make pitches and battle when you're not completely on your game," manager Ron Roenicke said.
The Reds counter with Mike Leake (7-8, 3.63), who is 0-1 with a 5.54 ERA in his last two starts. He's yielded 17 hits overall and four runs each in those two, most recently lasting seven innings Friday in a 4-3 loss to the New York Yankees.
Though the right-hander has a 4.99 ERA in five starts at Miller Park, he's 2-0 in those contests. For the second straight start at Milwaukee, Leake gave up four runs and nine hits in five innings of a 13-4 win June 15.
Cincinnati All-Star Todd Frazier batted .323 with six homers and 21 RBIs in the final 31 games prior to the break, but is 3 for 19 with a solo homer on the trip. He's 2 for 15 versus Lohse.
Braun is 1 for 9 with a homer against Leake.
Teammate Scooter Gennett is 4 for 9 versus Leake, but could sit after leaving Tuesday's game with tightness in his quad.