Washington Nationals First-Place Eliminiation Scenario
Washington must win 21 more games (59 total) to avoid elimination from first place.
Here are the final standings in a scenario in which Washington finishes in first place with 59 wins:

Team             W	L	PCT	GB
Washington       59	103	0.364	0.00
Philadelphia     59	103	0.364	0.00
Miami            58	104	0.358	1.00
Atlanta          58	104	0.358	1.00
New York         58	104	0.358	1.00

Tie breakers
Washington wins the series with Philadelphia 9 games to 4

To construct the scenario, we start with the current standings in the division:
Team             W	L	GL	PCT	GB
Philadelphia     54	39	69	0.581	0.0
New York         53	39	70	0.576	0.5
Miami            42	49	71	0.462	11.0
Atlanta          40	51	71	0.440	13.0
Washington       38	54	70	0.413	15.5

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

Atlanta currently has 2 win(s) against Miami and 3 loss(es).
Atlanta wins 4 additional game(s) against Miami and loses 4.
Atlanta loses the series 6 games to 7.
Atlanta wins 0 additional game(s) against teams outside the division and loses 46.

Atlanta currently has 5 win(s) against New York and 2 loss(es).
Atlanta wins 6 additional game(s) against New York and loses 0.
Atlanta wins the series 11 games to 2.
Atlanta wins 0 additional game(s) against teams outside the division and loses 46.

Atlanta currently has 4 win(s) against Philadelphia and 5 loss(es).
Atlanta wins 4 additional game(s) against Philadelphia and loses 0.
Atlanta wins the series 8 games to 5.
Atlanta wins 0 additional game(s) against teams outside the division and loses 46.

Atlanta currently has 3 win(s) against Washington and 3 loss(es).
Atlanta wins 4 additional game(s) against Washington and loses 3.
Atlanta wins the series 7 games to 6.
Atlanta wins 0 additional game(s) against teams outside the division and loses 46.

Miami currently has 2 win(s) against New York and 4 loss(es).
Miami wins 5 additional game(s) against New York and loses 2.
Miami wins the series 7 games to 6.
Miami wins 0 additional game(s) against teams outside the division and loses 43.

Miami currently has 2 win(s) against Philadelphia and 5 loss(es).
Miami wins 6 additional game(s) against Philadelphia and loses 0.
Miami wins the series 8 games to 5.
Miami wins 0 additional game(s) against teams outside the division and loses 43.

Miami currently has 5 win(s) against Washington and 1 loss(es).
Miami wins 1 additional game(s) against Washington and loses 6.
Miami loses the series 6 games to 7.
Miami wins 0 additional game(s) against teams outside the division and loses 43.

New York currently has 4 win(s) against Philadelphia and 2 loss(es).
New York wins 2 additional game(s) against Philadelphia and loses 5.
New York loses the series 6 games to 7.
New York wins 0 additional game(s) against teams outside the division and loses 44.

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

Philadelphia currently has 4 win(s) against Washington and 2 loss(es).
Philadelphia wins 0 additional game(s) against Washington and loses 7.
Philadelphia loses the series 4 games to 9.
Philadelphia wins 0 additional game(s) against teams outside the division and loses 45.

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