Danny Espinosa of the Nationals signs autographs before a home game against the Phillies this season. (Jonathan Newton/WASHINGTON POST)

Washington Nationals fans took back their ballpark from the invading fans of the Philadelphia Phillies on Friday night. And they did it by a landslide, not by some piddling plurality.

Then the Nats themselves, cheered on by a roaring crowd of 34,377, came from behind to beat Philadelphia, 4-3, in the bottom of the 11th inning, igniting an explosion of cheers and a throng of celebrating Nats surrounding pinch hitter Wilson Ramos near first base. As the last available healthy player on the Washington bench, Ramos knocked home the winning run with a bases-loaded single off Michael Schwimer to end a 3-hour 42-minute tingler.

The final run came out of nowhere, started by a two-out single by rookie Steve Lombardozzi for his third hit of the night. Six far more promising Nats rallies had already failed. But this time Bryce Harper drew his third walk of the game and Jayson Werth, after an awful 0-for-5 night, worked a full-count walk to bring up Ramos for his liner over the shortstop’s head.

As the Nats walked, or rather danced, off the field, an exact accounting of the true state of the crowd became apparent. Perhaps one in five fans trudged toward the exits in Phils gear. The remaining huge preponderance stood and cheered. And cheered as the PA pumped the moldy KC and the Sunshine Band chestnut “Get Down Tonight.”

All of this, accompanied by the early-season chills of the Nats’ MLB-leading fifth walk-off win of the season, raises a question as these teams prepare to meet twice more this weekend. The Nats have proved they can Take Back The Park. After this win, even more supporters may find their way out of the woodwork. Here’s the tough one: When, or will, the injured, stumbling 13-14 Phillies be able to Take Back First Place in the National League East from the team that now holds it? That would be the 17-9 Nats.

“Very refreshing,” Ian Desmond said of the crowd while Danny Espinosa added: “It’s awesome to have our own fans here. But there’s still definitely a vocal minority.” That includes a contingent by the right field bullpen that heckles Werth and likes to scream at Stephen Strasburg, as he warms up: “You’re going to blow out your shoulder.”

“You can still hear them, but it’s much different now,” said Strasburg, who allowed three runs in six innings and hit a double but left with a 3-2 deficit. He was saved from a defeat by a two-out, game-tying double by Jesus Flores in the eighth.

The Nats were acutely aware that the team’s marketing slogan, while ultimately helpful, also had the potential to backfire. “We almost had to win tonight,” said reliever Drew Storen, reduced to bench jockeying while still on the disabled list. “You get that turnout after kind of a controversial marketing campaign, you have to play to back it up.”

Baseball never ceases to obliterate our expectations. Washington fans come up big, but Strasburg gets knocked around and has to be saved from a defeat: You could’ve won my car and one of my family dogs on that parlay.

Nats fans dominated, both cheering and booing more loudly. Quick, get me oxygen, cheesesteak breath. Who knew the combo of hokey marketing and hometown pride still worked so well?

The crowd’s composition and behavior was also influenced by the Nats’ successful attempts to minimize package bus-tour tickets, keep Phils fans in small, separated groups and put on considerable extra security.

Before this game, Nats Manager Davey Johnson didn’t feel the need to psyche up his team and, in fact, removed one “Natitude” sign from behind home plate that he considered distracting to his pitchers. “I don’t have to tell ’em, ‘By the way, boys, the Phillies are coming to town.’ This is another opportunity to show our stuff,” Johnson said.

“If we win ballgames, that’s how we’re going to take this stadium back. We’ve got an attitude. I don’t know how to spell Natitude, but I don’t mind the attitude. The better the team you play, the more you better have it.”

Later this year, and perhaps for seasons to come, the rising Nationals and the clinging-to-the-top Phils are going to match talents and attitudes, toughness and health. By the second half of this year, if both heal, they may be classic duelists in a playoff chase.

“This is killing me,” said injured cleanup hitter Michael Morse, grinning but shaking his head. “All I want is for this to keep going so I can get back and be part of the fun.”

But for now, with both teams lacking so many heart-of-the-order hitters, this game was a determined, taut battle between what is left of the offenses of the Phils and Nats. That it went extra innings bespoke lost firepower for both.

“We’ve always had injuries. That’s part of baseball nowadays,” said Phils Manager Charlie Manuel, with emphasis on “nowadays” as if, in his time, there was a padlock on the training room door and a injury containing a words as obscure as “oblique” or hard to spell as “abdominal” probably shouldn’t bother a real major leaguer. “Some teams use those excuses. Our players don’t choose to think of it that way.”

The Phils’ grit is never challenged. The mettle of Nats fans sometimes is. In a role reversal, the Phils were booed when introduced, the Nats cheered. Incipient chants of “Lets Go Phils,” usually starting in the right field bleachers, were quickly drowned out with boos.

Washington’s demographic is No. 1 nationally in education and disposable income. But, as far as baseball is concerned, Nats crowds in some past years have cheered as though they’ve each brought along their personal dog-eared copy of Emily Dickinson’s collected poems and were working their way through “I like a look of agony because I know it’s true” during their team’s eternally fruitless pseudo-rallies.

In utter contrast, few fans of any team travel better (or worse) than those of the Phils, who carry copies of Attila the Hun’s four-word autobiography — “Outta My Way, Sucka.” They are loud, rude as needed, confident and feel deeply entitled to back their recent powerhouse of a team after generations of suffering and more than 10,000 defeats. Come on, setting aside the worst 5 or 10 percent of them, don’t Phils fans deserve their few years in the bright lights before their stars get older and the Nats, Braves and Marlins keep getting better?

No one knows when baseball tides change. But sometimes you can start to feel them shift. That began, between the Nats and Phils, late last year when the Nats under Johnson won “meaningless” series from the runaway 102-win Phils.

Now, those victories and the pride they bred in the team’s players and, perhaps, in its fans feel like a precursor. To what? The next two installments — of many — await us.

“Come enjoy the party,” said Storen, one of many Nats still smiling long after the game. Though barely.

For Thomas Boswell previous columns, visit washingtonpost.