From “Nights and Weekends” to “Happy Christmas” and “Drinking Buddies,” mumblecore master Joe Swanberg has shown a distinctive talent for infusing dazzling humanity and humor into simple stories. With his latest SXSW entry, “Win It All,” he does this in the tale of a lovable, low-grade degenerate whose offered an unusual opportunity to conquer his gambling addiction when thousands of dollars are dropped on his door step.

Thirty-something Eddie Garrett (Jake Johnson) spends his days working whatever random blue-collared job will take him on, and his nights gambling away his hard earned scratch at Chicago’s skeezier casinos. The guy’s never seen a hand of cards he could walk away from. Thus, his life has become a stunted cycle of win and lose, lose, lose. Then a loan sharking associate asks Eddie to guard a mysterious duffle bag for him while he serves a six-month prison sentence. For successful completion of this curious task, this smiling screw-up will be paid $10,000. All Eddie has to do is wait, and never open that bag.

Of course, he does. But Swanberg and Johnson build to this inevitable moment with a silly yet sincere sequence of drunkenness and melting resolve. With an effortless — albeit sketchy appeal — Johnson pokes and prods the bag, toying with its zipper, as he gawps at its emerging contents of rope, a dark t-shirt, and plastic binds. As soon as Eddie unloads a heap of rolled bills, we know where this is going. Yet this journey is not about the destination as much as the ride: rich with warmth, laughter, and ultimately hope.

At its core, “Win It All” is about whether or not people can truly change. Swanson suggests motivation is key. And for Eddie that motivation comes in the form of a lovely and lithe single-mom named Eva (Aislinn Derbez), who loves to dance and has no time to waste on a man unworthy of her. But earning a place in her world isn’t easy for Eddie.

Lower third titles of his wins and losses (+$2,148, -$27,300) become unexpected laugh lines, charting the money Eddie surrenders to his addiction and cruel hands of poker. Yet Swanberg has no interest in the game itself. There’s no steely tension pulled from bluffs, or claustrophobic close-ups of cards. This isn’t about the game. The focus is only on Eddie, his anxiety, his exaltation, his highs and lows. And we experience these with him as he bounces from back-alley games to heart-warming dates, then a gig at his brother’s lawn care company. There, Eddie digs in, and finally begins to make progress towards changing his ways, and paying back the thousands and thousands of dollars he steadily drained from that mystery bag. Then, he gets the call that its owner is getting out early, like in days not months. To save his future with Eva, Eddie must go all in with one last gamble.

Scruffy-faced and smiling that signature goofy grin through even Eddie’s bleakest moments, Johnson is perfectly cast as the screw-up we root for. His charisma is so easy and unpretentious that he feels like that drinking buddy you make as soon as your seat hits the bar stool. He’s got the gift of gab, and — just beneath the pain of his mistakes — a glimmer of hope that has you instantly and always on his side. And as Swanberg’s got an eye for casting, Johnson is surrounded by strong supporting players.

Derbez is delightful as the open-hearted Eva who gambles on Eddie. Keegan-Michael Key brings rueful guffaws and guidance as Eddie’s oft-frustrated Gamblers Anonymous sponsor. Joe Lo Truglio, best-known for broad comedies like “Wet Hot American Summer” and “Brooklyn Nine-Nine,” is surprisingly straight-faced and endearing as Eddie’s earnest older brother, who offers him advances, second chances, joints, and dad jokes. But even the smallest roles — including a cameo from Joe’s impossibly adorable little son Jude — add spirit to this deeply charming comedy.

“Win It All” might be Swanberg’s most accessible film yet. The awkwardness and improvised feel often associated with mumblecore is passed over for a tone and dialogue style that’s more polished, but no less impactful. In the hands of Hollywood, this gambler-centered movie would slide into slickness, glamor, and fantasy. Perhaps ending with a big heist or a rousing win win win! But Swanberg stays authentic, allowing Eddie to be the kind of affable jackass you can find on any shadier street. His ending is happy, but not Hollywood happy, more human happy. As a result, the film doesn’t feel like a fiction. Instead, it plays like one of those great stories you hear late night over beers, and marvel, thinking, “That’s so wild it can’t be true… But I hope it its.” [A-]

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