Joaquin Andujar pitched a three-hitter against Chicago and Lonnie Smith broke a one-for-16 slump with a run-scoring single to highlight a three-run fourth inning in St. Louis.
The victory, combined with New York's 2-1 triumph over Philadelphia, increased the Cardinals' lead over the Phillies in the National League East to 5 1/2 games and reduced their magic number for clinching their first division title to three. St. Louis has seven games left and Philadelphia has eight.
Andujar (15-10), won his seventh straight decision, gave up a run in the ninth on an RBI double by Mel Hall, who had two of the three Chicago hits. Andujar retired 14 batters on grounders to go with three strikeouts in extending the Cubs' losing streak to four games.
In his seven straight victories, Andujar has allowed seven runs.
"We have harmony on this ball club," said Andujar. "Everbody's happy. Whitey Herzog keeps it that way."
The Cardinals took a 1-0 lead in the first when Smith walked, stole second, moved to third on a grounder and scored on George Hendrick's two-out single.
Consecutive singles by Willie McGee, Ken Oberkfell and Tom Herr in the fourth increased the lead to 2-0 and the Cardinals added another run on a throwing error by shortstop Junior Kennedy before Smith's single knocked out starter Dickie Noles (9-13) and made the score 4-0.
The Cardinals added their final run in the eighth on back-to-back doubles by Oberkfell and Herr.