"There's no vanity with Chan," says Amanda Seyfried, who plays his love interest in Dear John, based on the Nicholas Sparks novel. "That's the first thing that struck me about him. I saw this intensely good-looking guy, and I expected some vanity. But he's not like that at all. He's not afraid to be embarrassed, not afraid to look stupid. One of the reasons he's such a good actor is that he's not afraid of anything."

To be fair, the jury's still out on how good an actor Channing Tatum really is, will be, or, in green-screen gunk like G.I. Joe, even needs to be. G.I. Joe may have certified Tatum as a box-office draw—it was his first $100 million earner—but his strongest performance to date came in his breakthrough role. In 2006's outer-borough coming-of-age tale A Guide to Recognizing Your Saints, Tatum played a street tough named Antonio, a pained, charismatic, and brutish dead-ender who thinks only with his fists. The New York Times compared him to Brando; the film's director, Dito Montiel, tosses out McQueen, Pacino, De Niro. "There's something about Chan that feels normal," says Montiel, a no-bullshit dems/dese/dose guy who has cast Tatum in all three of his films. "Most actors today live in a bubble. Chan's a real guy. He's had his ass kicked in real life, and done a little of that, too. That changes you."

Tatum's considerable onscreen presence is still mostly physical. "I've aways been good at picking up certain things, like sports and dancing," he says. In his films, Tatum oozes a jock's bulletproof confidence, but because real men don't swagger, he often undercuts his virility with barn-size gestures of small-town goodness: unfailing manners, aw-shucks humility, courtliness toward women. Tatum calls Clint Eastwood his hero; he says he used to dream about writing a letter to him: "I'm sorry for all of us wimpy actors out there. Please teach me." Not surprisingly, then, a Channing Tatum character usually isn't much of a talker. He admits he tends to mumble his lines. "I had a bad stutter when I was really young," he says. "I couldn't get a sentence out. Like, 'D-d-d-d-d-d-d-d-ad.' And that turned into a mumble."

Tatum's father, himself a blue-chip athlete in high school, owned a roofing company until he fell and broke his back; after that, he traveled the South by car, peddling building supplies. The family moved from Alabama to Mississippi's Gulf Coast and finally to Tampa, Florida, where Chan lived out the script to a Very Special Degrassi High episode: excelling as captain of the football team, exchanging promise rings with the head cheerleader, and fending off thoughts about suicide, a side effect of medication he took to treat attention-deficit disorder.

"I was not good in school," Tatum says. "I could never read very fast or very well. I got tested for learning disabilities, for dyslexia. Then I got put on Ritalin and Dexedrine. I took those starting in the eighth grade." The pills worked, too, for a while. "As soon as they pumped that drug into me, it would focus me right in," he exclaims. "I was doing great. I was getting A's, doing extra-credit work!" He laughs, then asks if I need another beer. "But the longer I took the Dexedrine," he continues, "the worse I felt. It sucked all the personality from me. I'd get depressed. I would think suicidal—I was never personally suicidal, but I could see how some kids were, how they'd be, like, I can't take this anymore. Finally, my senior year, I said, 'That's it. I am done with these.'"