Chicago Cubs First-Place Eliminiation Scenario
Chicago must win 14 more games (63 total) to avoid elimination from first place.
Here are the final standings in a scenario in which Chicago finishes in first place with 63 wins:

Team             W	L	PCT	GB
Chicago          63	99	0.389	0.00
Pittsburgh       63	99	0.389	0.00
St. Louis        63	99	0.389	0.00
Cincinnati       63	99	0.389	0.00
Milwaukee        62	100	0.383	1.00

Tie breakers
Chicago wins the series with Cincinnati 8 games to 5
Chicago wins the series with Pittsburgh 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        59	43	60	0.578	0.0
St. Louis        53	49	60	0.520	6.0
Pittsburgh       52	50	60	0.510	7.0
Cincinnati       49	53	60	0.480	10.0
Chicago          49	55	58	0.471	11.0

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

Chicago currently has 2 win(s) against Cincinnati and 5 loss(es).
Chicago wins 6 additional game(s) against Cincinnati and loses 0.
Chicago wins the series 8 games to 5.
Chicago wins 0 additional game(s) against teams outside the division and loses 42.

Chicago currently has 5 win(s) against Milwaukee and 8 loss(es).
Chicago and Milwaukee have no remaining games.
Chicago loses the series 5 games to 8.
Chicago wins 0 additional game(s) against teams outside the division and loses 42.

Chicago currently has 3 win(s) against Pittsburgh and 4 loss(es).
Chicago wins 4 additional game(s) against Pittsburgh and loses 2.
Chicago wins the series 7 games to 6.
Chicago wins 0 additional game(s) against teams outside the division and loses 42.

Chicago currently has 3 win(s) against St. Louis and 6 loss(es).
Chicago wins 4 additional game(s) against St. Louis and loses 0.
Chicago wins the series 7 games to 6.
Chicago wins 0 additional game(s) against teams outside the division and loses 42.

Cincinnati currently has 2 win(s) against Milwaukee and 4 loss(es).
Cincinnati wins 7 additional game(s) against Milwaukee and loses 0.
Cincinnati wins the series 9 games to 4.
Cincinnati wins 1 additional game(s) against teams outside the division and loses 33.

Cincinnati currently has 2 win(s) against Pittsburgh and 4 loss(es).
Cincinnati wins 4 additional game(s) against Pittsburgh and loses 3.
Cincinnati loses the series 6 games to 7.
Cincinnati wins 1 additional game(s) against teams outside the division and loses 33.

Cincinnati currently has 3 win(s) against St. Louis and 4 loss(es).
Cincinnati wins 2 additional game(s) against St. Louis and loses 4.
Cincinnati loses the series 5 games to 8.
Cincinnati wins 1 additional game(s) against teams outside the division and loses 33.

Milwaukee currently has 5 win(s) against Pittsburgh and 5 loss(es).
Milwaukee wins 2 additional game(s) against Pittsburgh and loses 1.
Milwaukee wins the series 7 games to 6.
Milwaukee wins 0 additional game(s) against teams outside the division and loses 44.

Milwaukee currently has 6 win(s) against St. Louis and 1 loss(es).
Milwaukee wins 1 additional game(s) against St. Louis and loses 5.
Milwaukee wins the series 7 games to 6.
Milwaukee wins 0 additional game(s) against teams outside the division and loses 44.

Pittsburgh currently has 4 win(s) against St. Louis and 5 loss(es).
Pittsburgh wins 4 additional game(s) against St. Louis and loses 0.
Pittsburgh wins the series 8 games to 5.
Pittsburgh wins 1 additional game(s) against teams outside the division and loses 39.

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