WASHINGTON — It was merely the first inning, yet fans kept rising out of their seats to applaud or yell or twirl their red towels, to chant “Let’s go, Nats!” and “M-V-P!” and various players’ names, enjoying every moment of a seven-run outburst that would, eventually, propel their city to its first World Series appearance in 86 years.

And then, a couple of hours and several innings later, as the Washington Nationals were protecting a shrinking lead, those same spectators, 43,976 strong, stood and shouted and reveled some more Tuesday night, giddily counting down the outs needed to finish off an NL Championship Series sweep of the St. Louis Cardinals.

From 19-31 during a mediocre May to the Fall Classic in an outstanding October.

Extending their stunning turnaround, the wild-card Nationals got RBIs from middle-of-the-order stars Anthony Rendon and Juan Soto in that breakout first inning, and Patrick Corbin’s 12-strikeout performance and a trio of relievers helped hold on to beat St. Louis 7-4 in Game 4 of a lopsided best-of-seven NLCS.

Now the Nationals get plenty of time to rest and set up their rotation before beginning the World Series in a week against the Houston Astros or New York Yankees. Houston leads the best-of-seven AL Championship Series 2-1 after winning Game 3 at New York 4-1 Tuesday.

Second-year manager Dave Martinez — who so many folks thought might be fired back in May — turned to his NL-worst bullpen, such a problem for so much of this season.

After Tanner Rainey got three outs, and Sean Doolittle got five, Daniel Hudson came in for his fourth save in four chances this postseason.