Chicago Cubs First-Place Eliminiation Scenario
Chicago must win 25 more games (36 total) to avoid elimination from first place.
Here are the final standings in a scenario in which Chicago finishes in first place with 36 wins:

Team             W	L	PCT	GB
Chicago          36	126	0.222	0.00
St. Louis        36	126	0.222	0.00
Cincinnati       36	126	0.222	0.00
Milwaukee        36	126	0.222	0.00
Pittsburgh       35	127	0.216	1.00

Tie breakers
Chicago wins the series with Cincinnati 7 games to 6
Chicago wins the series with Milwaukee 7 games to 6
Chicago wins the series with St. Louis 7 games to 6

To construct the scenario, we start with the current standings in the division:
Team             W	L	GL	PCT	GB
Milwaukee        11	6	145	0.647	0.0
Chicago          11	7	144	0.611	0.5
Pittsburgh       11	8	143	0.579	1.0
Cincinnati       9	9	144	0.500	2.5
St. Louis        9	10	143	0.474	3.0

Next, we show how the remaining series of games plays out in the scenario:

Chicago currently has 0 win(s) against Cincinnati and 0 loss(es).
Chicago wins 7 additional game(s) against Cincinnati and loses 6.
Chicago wins the series 7 games to 6.
Chicago wins 0 additional game(s) against teams outside the division and loses 92.

Chicago currently has 0 win(s) against Milwaukee and 0 loss(es).
Chicago wins 7 additional game(s) against Milwaukee and loses 6.
Chicago wins the series 7 games to 6.
Chicago wins 0 additional game(s) against teams outside the division and loses 92.

Chicago currently has 0 win(s) against Pittsburgh and 0 loss(es).
Chicago wins 4 additional game(s) against Pittsburgh and loses 9.
Chicago loses the series 4 games to 9.
Chicago wins 0 additional game(s) against teams outside the division and loses 92.

Chicago currently has 0 win(s) against St. Louis and 0 loss(es).
Chicago wins 7 additional game(s) against St. Louis and loses 6.
Chicago wins the series 7 games to 6.
Chicago wins 0 additional game(s) against teams outside the division and loses 92.

Cincinnati currently has 1 win(s) against Milwaukee and 2 loss(es).
Cincinnati wins 10 additional game(s) against Milwaukee and loses 0.
Cincinnati wins the series 11 games to 2.
Cincinnati wins 0 additional game(s) against teams outside the division and loses 95.

Cincinnati currently has 0 win(s) against Pittsburgh and 0 loss(es).
Cincinnati wins 7 additional game(s) against Pittsburgh and loses 6.
Cincinnati wins the series 7 games to 6.
Cincinnati wins 0 additional game(s) against teams outside the division and loses 95.

Cincinnati currently has 0 win(s) against St. Louis and 0 loss(es).
Cincinnati wins 4 additional game(s) against St. Louis and loses 9.
Cincinnati loses the series 4 games to 9.
Cincinnati wins 0 additional game(s) against teams outside the division and loses 95.

Milwaukee currently has 0 win(s) against Pittsburgh and 0 loss(es).
Milwaukee wins 13 additional game(s) against Pittsburgh and loses 0.
Milwaukee wins the series 13 games to 0.
Milwaukee wins 1 additional game(s) against teams outside the division and loses 95.

Milwaukee currently has 0 win(s) against St. Louis and 0 loss(es).
Milwaukee wins 5 additional game(s) against St. Louis and loses 8.
Milwaukee loses the series 5 games to 8.
Milwaukee wins 1 additional game(s) against teams outside the division and loses 95.

Pittsburgh currently has 0 win(s) against St. Louis and 0 loss(es).
Pittsburgh wins 9 additional game(s) against St. Louis and loses 4.
Pittsburgh wins the series 9 games to 4.
Pittsburgh wins 0 additional game(s) against teams outside the division and loses 91.

# Chicago Cubs' magic number
# Chicago's magic number
# Cubs' magic number
# MLB Playoff Race