Ramirez went 3-for-5 and knocked in four, Mark Lamb stroked a key pinch-hit, two-run double, and Gaby Sanchez ended with a pair of hits and an RBI for the Marlins, who took the rubber match of a three-game set.
Johnson (3-1) yielded two runs on three hits while striking out eight and walking four. He upped his lifetime record against the Nationals to 6-0.
The Nats got RBI from Ian Desmond and Adam Dunn. Washington starter John Lannan (1-2) surrendered nine hits, six runs and three walks over five innings in the setback.