Correction: A previous version of this article incorrectly described the team’s “magic number” at that point. The version said that any combination of Nationals wins and Atlanta Braves losses equaling 11 would give Washington the National League East title. In fact, the number represented the combination required to eliminate the Braves from contention. The Philadelphia Phillies still had a mathematical chance to win the division, though they no longer do. This version has been updated. 

Since professional baseball returned to Washington seven years ago — heck, even when it was here all those miserable decades before that — there has been precious little magic surrounding the local team. In Septembers past, the Washington Nationals would be part of pennant race baseball only tangentially, beating one team that was contending, rolling over for another, on the fringes of the sport’s most riveting time of year. Irrelevance outweighed tension, time after time.

But this week, the Nationals are entering territory that has not been part of a reasonable discussion in Washington since the Great Depression. By sweeping the New York Mets last week, they dropped their magic number (and we’ll get to what this is) for eliminating the Atlanta Braves from contention to 11 games. Eleven measly games.

They have 17 to play. They lead the Braves, their closest pursuers, by 61 / 2 games in the standings — and the Braves needed to win Friday night and Saturday afternoon to get that close. The division championship, and the corresponding spot in the playoffs, is edging tantalizingly close — close enough that, at some point during a seven-game homestand that begins Tuesday, a crowd at Nationals Park might be looking down on a hugging group of players, celebrating along with them, champagne to come. And that means fall could be fundamentally altered in Washington, where “autumn” and “Redskins season” have been synonymous since 1937.

In other cities, Boston or Philadelphia or New York — especially New York — such a baseball story line could be something of an expectation. But here in poor, poor Washington, this is all so new.

Consider: The District’s major league team, when it was officially dubbed the Senators, last won its league (American) in a year (1933) when Franklin D. Roosevelt was was serving the first of his four presidential terms. Over the next 27 seasons, that same franchise posted all of four winning seasons. (By way of comparison, those Senators lost 95 or more games five times.) The cumulative winning percentage over that time: .447.

That team, mercifully to some, left town and became the Minnesota Twins. It was immediately replaced by an expansion outfit that was no better. In the next 11 seasons, there were 10 losers and one winner. The franchise bolted to Texas. Thus, 38 seasons in which the Senators lost 797 more games than they won and never reached the postseason were followed by 33 summers without any baseball at all.

Which was worse? Hard to say. In 2005, when the Expos relocated from Montreal and became the Nationals, they finished an even 81-81. But given how it happened — an enthralling first half of the season in which they went 50-31, followed by a collapse in the second half in which they went, symmetrically and painfully, 31-50 — it was difficult.

Some fan bases will tell you they have endured more misery. But think about it: There are 30 major league franchises representing 28 cities. The city with the next-longest postseason drought is Kansas City, where the Royals won the World Series in 1985 and haven’t made the playoffs since. Washington has a 53-year (dis)advantage on that.

Similarly, the ballads of the Pirates (no winning seasons since 1992), the Cubs (no World Series titles since 1908), the Indians (no World Series titles since 1948) are tried and true, part of baseball lore and the fabric of Pittsburgh, Chicago and Cleveland, respectively. But middle-aged Pittsburghers still have the “We Are Family” Pirates of 1979, world champions. They still have Roberto Clemente and Willie Stargell, Hall of Famers. Clevelanders have seven postseason appearances since 1995 alone. They have Bob Feller and Roberto Alomar, Hall of Famers. Cubs fans, for all their over-documented heartache, have 25 winning seasons since 1933.

What does Washington have? Walter Johnson and the 1924 World Series championship, and the group that won the American League but lost the Series the year after. Joe Cronin and the 1933 American League pennant, a team that lost the Series in five games to the New York Giants. And that’s about it.

So it was odd earlier in the week, when the Nationals completed their sweep of the Mets, to listen to players in the visiting clubhouse at Citi Field trying to downplay what was in the process of happening. The Nationals not only hold a commanding lead over the Braves, they have the best record in baseball.

“I don’t even know what the lead is, to tell you the truth,” third baseman Ryan Zimmerman said.

On that night, it had grown to 81 / 2 games. And the “magic number” dropped to 11.

That number will continue appear on the Post’s front page until the Nationals clinch the division. (Yes, we know this could be seen as a jinx. But dream for a minute.)

Here’s the formula: G + 1 - W(a) - L(b) where G is the total number of games in the season (162), W(a) is the number of wins for the team in first place and L(b) is the number of losses for the team in second. After the Nationals’ 5-4 loss Saturday, W(a) is 89 (and a Washington team hasn’t won 90 games since those 1933 Senators). L(b) is 63, the Braves’ losses. And the equation becomes 162 + 1 - 89 - 63 = 11.

The way to think of what’s to come, as the Nationals play one more game in Atlanta Sunday night before returning home to face the Los Angeles Dodgers and Milwaukee Brewers, is that any combination of Braves losses and Nationals wins equaling 11 will mathematically eliminate the Braves from contention. With each Nats win, the number will go down one. With each Braves loss, it will go down one more — with the outside possibility that the Philadelphia Phillies, should they overtake the Braves, could affect the number as well.

There is scant evidence that, 79 years ago, the phrase “magic number” existed. In 1933, as the Senators closed in on the American League pennant, the Post noted that “Only four more victories in their remaining 11 games are needed by the Nats to clinch the pennant beyond mathematical doubt, even if the Yankees should win all of their 15 remaining games.”

That, then, is the number accompanying this story explained. Barring something unexpected, it should decrease over the next week. If and when it hits zero, hang on — because Washington will be in for something it hasn’t experienced in nearly eight decades.