The Post Sports Live crew tries to see meaning in the Nationals late season run even though the team is a longshot to make the playoffs. (Post Sports Live/The Washington Post)

The greatest day-after-day drama in American sports is the near-miracle come-from-behind September baseball chase with the postseason at stake. No living Washington baseball fan has experienced it. Since such quests are ridiculously unlikely, the magnificent monster doesn’t seem completely real, even as it grows before your eyes, until suddenly there is a day when you say, “Holy [expletive of your choice], it actually happened!”

That day has not arrived for a Nationals team that was 101 / 2 games out of the last wild-card spot just 37 games ago. And before this Nats’ homestand is over on Sunday, the chances of its arrival could go from slim to nil. But for a moment on Tuesday, as Denard Span’s groundball darted between the legs of shortstop Andrelton Simmons into center field and two runs scored for a walk-off win, the thought of such a season crossed every mind.

Just as it seemed the Nats had squandered a vital win, blowing a late lead, they suddenly scored three unlikely runs in the bottom of the ninth inning for a 6-5 win over Craig Kimbrel, the toughest closer in baseball. And they did it without hitting a ball solidly. With two walks and three routine grounders, a couple of them with eyes, the Nats perpetrated the sort of baseball magic that inspires teams to dream.

“Little rewrite problem?” Manager Davey Johnson asked, laughing.

Will this be a rewrite of one game or, eventually, of a whole season?

It only took five hours to get the next few paragraphs of the tale. In the second game of a split doubleheader, the Nats won a brilliantly pitched 4-0 game to sweep their Atlanta nemesis that had won 12 of 16 previous head-to-head games. Tanner Roark, 27 next month, who seemed locked in AAA in perpetuity, continued his dazzling debut season with seven scoreless two-hit innings, lowering his ERA to 1.08 in 412 / 3 innings and building his record to 7-0. Ryan Zimmerman’s ninth-inning solo homer was followed by RBI hits by Ian Desmond and Adam LaRoche.

Thus, despite a Reds slaughter of the Astros, the Nats still cut their deficit in the wild-card chase to 41 / 2 games while winning 21 of their last 27 games.

This entire day may ultimately fall into the thrilling “fleeting hope” category. But for a few thousand fans that came to an often-subdued afternoon game that began with a moment of silence for the victims of the Navy Yard mass murder, the opening victory was a glimpse of what a 100-to-1 comeback feels like. Some season in their future the Nats will probably do such a thing. But this year?

After Span’s bouncer, which should have tied the game but not won it, the Nats celebrated all over the infield as if they had won a postseason game. Maybe they were acting silly. Or maybe that’s the essence of what baseball momentum actually is. A sport of superstitions and hot streaks carries you, even forgives your mistakes, just as the opposite momentum stomped the Nats during an 8-18 crash in midseason.

Several weeks ago, Jayson Werth said: “Playing from ahead is tough. Playing from behind is the best.” What were jittery nerves for four months become focused by the threat of elimination. Every day feels like a playoff game. Then, if you win 27 of 37 as the Nats have, you look at the 11 games left and say, “Win ’em all. See how the Reds like that.”

Cincinnati can still put a noose around the Nats necks if they finish 5-5 for 91 wins. The Nats would need to finish 10-1 just to tie. But the history of such chases is that the leader seldom plays comfy .500 ball. They either blitz your hopes with a killing win streak or else collapse back into your arms, like Texas that led the AL West until the Rangers’ current 2-12 collapse put them 61 / 2 games behind the A’s.

“There are teams that get hot early or get hot in the middle,” Desmond said. “We’re a team that got hot late. We never stopped grinding. We’re the same group. . . . By no means are we near the pot of gold at the end of the rainbow. But we are playing better.”

The Game 1 win carried extra emotional weight because the Nats tried to give the game away in the same careless, fundamentally flawed ways they wasted wins as they fell to 54-60. After taking a 3-0 lead in the first inning, they never added a tack-on run. Tyler Clippard committed two cardinal sins in the eighth with a 3-2 lead. First, he walked a man. Then he threw an 0-2 fastball over the plate to wild-swinging strikeout machine Evan Gattis, who swatted the gift into the center field bleachers for a 4-3 Atlanta lead.

Even worse was the gift insurance run the Nats handed the Braves in the ninth. Bryce Harper, who’s made several spectacular throws recently, but all to the proper bases in appropriate situations, suddenly lost his mind on a single to left by Eliot Johnson. He unleashed a 300-foot throw to first, trying to double off Johnson. The ball ended where it deserved to go — by the box seats as Johnson took second. That extra base led to a run when Desmond booted a routine five-hopper with two outs. A fan in Nats gear in the upper deck bellowed, “Suck it up and stop choking.”

In a meaner baseball town, those words would’ve been heard many times by now. Or perhaps the small crowd just made them audible.

“We gave [the game] to them,” Johnson said. “Harper, I don’t know what he’s thinking. . . . He knows [he’s wrong] but he’s still going to hear it.”

But September intervened. Strange things happen this time of year. On Sunday the Reds seemed like a sure winner in Milwaukee, up four runs late against the lowly Brewers. Then Milwaukee rallied to tie. Carlos Gomez robbed the Reds of a three-run homer in the top of the ninth, then the Brewers had their own walk-off homer in the bottom of the ninth.

For epic late comebacks to be completed, like the ’04 Astros, the ’07 Rockies and Phillies or the ’11 Cards and Rays, the leader must have at least two or three unbelievable losses and the chaser a roughly equal number of insane victories.

Many Nats felt ambivalent about playing such a vital game and celebrating so joyously just 29 hours and four blocks away from a senseless slaughter that has horrified the nation.

The Nats wore their “patriotic blue” uniforms in honor of the Navy and had a pregame visit from an admiral. Before the game, they were as troubled as other Washingtonians. But compartmentalizing, whether it’s good for the soul or not, is an athletic necessity.

“Even when there are tragedies in your own family, the field is like a sanctuary for us,” Desmond said. “All things leave your mind.”

Now, only one thing is on the Nats’ minds. “After we gave up that extra run I thought, ‘It’s not going to be too good for us,’ ” Span said. Then things that just don’t happen, happened. Kimbrel walked a leadoff man. Wilson Ramos hit a chop behind second on which Johnson had an easy flip to force slow LaRoche. But he didn’t realize who was running and tried a crazy back-hand glove flip that was off target. Anthony Rendon squared to sacrifice bunt and give away an out four times; but he got two strikes, was forced to hit and ended up with a walk to load the bases.

With two strikes, Chad Tracy poked a puny ground out to first base, yet it advanced all three runners. Then, with the infield back, Atlanta got an outcome it would have accepted — a game-tying groundout by Span. But Simmons, a brilliant fielder, butchered it.

“They’ve broken our hearts all year,” said Span. “Right now we just keep fighting. It’s almost like we have to be flawless these last two weeks.”

Or, as they were on Tuesday, both good and lucky, too.

Time to call for rewrite? Not yet, not nearly. But, in case that day doesn’t arrive, at least the ninth inning of this game gave Washington a hint of how it feels. Well, if you multiplied the emotion by a thousand.

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