In "The Gambler," Mark Wahlberg plays a college professor with a near-suicidal addiction to gambling. Half of that sounds right up his alley; but the other half, he knew, might be tougher.

He expected that moviegoers would have little trouble buying into him as a guy with an obsession for blackjack. But as an actor famed for his "blue-collar types," could he sell them on the "day job" side of his character?

"You need to challenge yourself and surprise audiences," Wahlberg said. "People have me figured out? Mix it up on them. I jumped at this chance. That meant committing to being the most prepared I've probably ever been on a set. I had to, just to be believable. I mean, me as a college professor? I read with some professors, went to lectures, got a taste of how they hold a class."

Jim Bennett, his character, teaches literature and quotes Shakespeare. He once published a novel, but now he's lost, sure of only one thing: He's headed for mediocrity.

Wahlberg figured that he'd have to master screenwriter William Monahan's dialogue to have a prayer of being convincing in the part. Whatever other prep he did would not matter as much as having Monahan's lines "trippingly on the tongue," as Shakespeare's Hamlet put it.

"The first lecture alone was 14 pages, basically just a long, long monologue," Wahlberg recalled. "I had to know that, inside and out, because I couldn't be referring back to the script. Know that scene, all those pages, and you know the character. That was key.

"And we shot that scene first, the first day of filming. I 'knew' him by the end of that day. We just dove right in. That's the hardest scene for me in the film, but why not? Let's get the heavy lifting out of the way."

'Thrill' seekers

The actor loved "the way the script sounds. Monahan writes scripts that are 'writer's piece' movies. Everybody in the movie — John Goodman [as a quotably clever loan shark], all of us — got drawn in by that."

Wahlberg, 43, who finished his high school degree only last year, insisted that the real "stretch" for him in "The Gambler" is the actual gambling. Whatever you might guess about the movie star, rolling the dice in Vegas with his "entourage" is not his thing.

"I try to refrain," he said. "I do. I try to make the only times I bet be when there's a repeat of a fight on TV, and I can talk one of my friends into betting on the loser. I like sure things, knowing I'm gonna win."

He doesn't refrain from other types of bets, however.

"I do gamble on myself every day in my career. I make the wrong bet and lose, I have nobody to blame but myself."

He gets why people gamble. "The thrill. You know, in the original version of 'The Gambler' [1974], Jimmy Caan's character only feels alive in that instant, waiting for the dice to stop rolling, the roulette wheel to stop, for that last card to turn over."

But there's another way the addiction manifests itself. Jim Bennett "is trying to strip himself of everything positive in his life. … He's not the kind of guy who will do himself in. But he's not bothered all that much about putting these loan sharks in a position to do some harm to him."

Seeking pardon

Wahlberg has been in the headlines over his efforts to be pardoned for assault and other crimes he committed in Massachusetts in the 1980s when he was a teenager. He caught some flak for asking for the pardon, but got a break when his most prominent victim, a man named Johnny Trinh, came out in favor of the pardon.

There were reports that Wahlberg had blinded Trihn in an assault in 1988, but Trihn told the Washington Post that Wahlberg "was not responsible for that. … My left eye was already gone."

Wahlberg took a deep breath and sighed.

"What a weight lifted off my shoulders, to realize that I didn't cause this horrible injury to him," he said. "I have carried that guilt for years and years and years. That is such an act of graciousness, him saying that.

"But look, I've lived my life ever since trying to better myself as a person, to do right, knowing that I've caused pain and grief. That's what I will continue to do whether I receive a pardon or not. I teach my kids, it's about giving back until you get a second chance. I got my diploma, just so I could show my kids that self-improvement never stops. You stick with it.

"So, pardon or not, I'm in a good place."