Washington ace Gio Gonzalez tallied his major league-leading 21st win of the season, lasting six innings and allowing three earned runs on six hits and three walks while recording six strikeouts.
The win as the Nationals' 95th of the season, tying the 1979 Montreal Expos for most franchise victories in a season and becoming the first Washington team to win 95 games since 1933.
Cloyd (L, 2-2) left the game after throwing five innings and getting knocked around for six hits and six earned runs.
Following a bases-clearing three RBI double by left fielder Darin Ruf in the bottom of the first that gave Philadelphia the 3-1 lead, Nationals left fielder Michael Morse collected the first of his four RBI on the night when he launched a solo homer in the second. Morse would later belt his second home run of the night, a two-run shot, in the sixth.
The Nationals took the lead for good on a RBI single from Harper that scored second baseman Danny Espinosa in the fifth inning.