Washington were 3-0 down at the top of the fifth inning but three unanswered runs in the seventh lifted the Nationals to victory over the free-falling Rockies at Coors Field.
After two runs in the fifth inning and another two in the sixth, Adam LaRoche hit a tie-breaking homer in the seventh as the National League (NL) East division-leading Nationals won their fourth straight game.
The Nationals (55-43), who condemned the Rockies to a seventh consecutive defeat, have now pulled two games clear in the NL East following the Atlanta Braves' 6-5 loss to the Miami Marlins.
At Wrigley Field, the Chicago Cubs shutout the San Diego Padres for a 6-0 win.
The triumph, set-up by Anthony Rizzo's two home runs, also snapped the Cubs' five-game losing streak.
In other results on Tuesday, the Tampa Bay Rays maintained their good form with a 7-2 win against the St Louis Cardinals.
Yunel Escobar had a two-run double, while Jake Odorizzi allowed two runs as the Rays won a season-high six consecutive game.
The Toronto Blue Jays bounced back from Monday's poor effort, downing the Boston Red Sox 7-3.
Toronto (52-49) were unable to make any significant inroads in the American League East division, however, after the Baltimore Orioles accounted for the Los Angeles Angels 4-2.
The Orioles (54-44) are three-and-a-half games clear of the Blue Jays and the New York Yankees, who were 2-1 winners over the Texas Rangers.
Mike Moustakas homered twice as the Kansas City Royals upstaged the Chicago White Sox 7-1, while the Pittsburgh Pirates defeated the Los Angeles Dodgers 12-7.
The San Francisco Giants were 9-6 victors against the Philadelphia Phillies, while the Cleveland Indians eased past the Minnesota Twins 8-2.
Elsewhere, the Cincinnati Reds slumped to a fifth straight defeat - losing 4-3 to the Milwaukee Brewers.
The New York Mets overcame the Seattle Mariners 3-1 and the Detroit Tigers were beaten 5-4 by the Arizona Diamondbacks.
Meanwhile, the Houston Astros prevailed 3-2 against the Oakland Athletics after a 12th inning.