Washington Nationals First-Place Elimination Scenario
Washington must win 18 more games (81 total) to avoid elimination from first place.
Here are the final standings in a scenario in which Washington finishes in first place with 81 wins:

Team             W	L	PCT	GB
Washington       81	81	0.500	0.00
Philadelphia     80	82	0.494	1.00
Atlanta          80	82	0.494	1.00
Miami            79	83	0.488	2.00
NYMets           73	89	0.451	8.00

To construct the scenario, we start with the current standings in the division:
Team             W	L	GL	PCT	GB
Atlanta          79	55	28	0.590	0.0
Philadelphia     74	60	28	0.552	5.0
Miami            68	66	28	0.507	11.0
Washington       63	73	26	0.463	17.0
NYMets           60	74	28	0.448	19.0

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

Atlanta currently has 8 win(s) against Miami and 2 loss(es).
Atlanta wins 0 additional game(s) against Miami and loses 3.
Atlanta wins the series 8 games to 5.
Atlanta wins 0 additional game(s) against teams outside the division and loses 16.

Atlanta currently has 6 win(s) against NYMets and 7 loss(es).
Atlanta and NYMets have no remaining games.
Atlanta loses the series 6 games to 7.
Atlanta wins 0 additional game(s) against teams outside the division and loses 16.

Atlanta currently has 5 win(s) against Philadelphia and 1 loss(es).
Atlanta wins 1 additional game(s) against Philadelphia and loses 6.
Atlanta loses the series 6 games to 7.
Atlanta wins 0 additional game(s) against teams outside the division and loses 16.

Atlanta currently has 8 win(s) against Washington and 3 loss(es).
Atlanta wins 0 additional game(s) against Washington and loses 2.
Atlanta wins the series 8 games to 5.
Atlanta wins 0 additional game(s) against teams outside the division and loses 16.

Miami currently has 6 win(s) against NYMets and 4 loss(es).
Miami wins 2 additional game(s) against NYMets and loses 1.
Miami wins the series 8 games to 5.
Miami wins 6 additional game(s) against teams outside the division and loses 12.

Miami currently has 5 win(s) against Philadelphia and 8 loss(es).
Miami and Philadelphia have no remaining games.
Miami loses the series 5 games to 8.
Miami wins 6 additional game(s) against teams outside the division and loses 12.

Miami currently has 8 win(s) against Washington and 1 loss(es).
Miami wins 0 additional game(s) against Washington and loses 4.
Miami wins the series 8 games to 5.
Miami wins 6 additional game(s) against teams outside the division and loses 12.

NYMets currently has 4 win(s) against Philadelphia and 5 loss(es).
NYMets wins 4 additional game(s) against Philadelphia and loses 0.
NYMets wins the series 8 games to 5.
NYMets wins 7 additional game(s) against teams outside the division and loses 11.

NYMets currently has 6 win(s) against Washington and 4 loss(es).
NYMets wins 1 additional game(s) against Washington and loses 2.
NYMets wins the series 7 games to 6.
NYMets wins 7 additional game(s) against teams outside the division and loses 11.

Philadelphia currently has 8 win(s) against Washington and 3 loss(es).
Philadelphia wins 0 additional game(s) against Washington and loses 2.
Philadelphia wins the series 8 games to 5.
Philadelphia wins 0 additional game(s) against teams outside the division and loses 15.

# Washington Nationals' magic number
# Washington's magic number
# Nationals' magic number
# MLB Playoff Race