Luis Arraez reached on a leadoff single in the third inning before Soler connected against Trevor Williams, giving Miami a 2-1 lead. It was Soler's 19th go-ahead homer of the season, extending his major league lead.
Jacob Stallings had two hits for the Marlins, who had dropped six of seven to fall back to .500.
Washington wasted a strong performance by Williams (6-8), who allowed five hits and walked two in seven innings. The Nationals had won five of six.
Washington threatened in the ninth against Tanner Scott. Keibert Ruiz and Ildemaro Vargas hit one-out singles, but Scott retired Jacob Young on a double-play grounder for his third save in five opportunities.
Scott replaced David Robertson as Miami’s closer after Robertson squandered a 2-1 lead Saturday. It was Robertson’s third blown save since the Marlins acquired the veteran reliever from the New York Mets on July 29.
The Associated Press