"If you had asked me five or six weeks ago, 100% I would have said Crystal. But now I've changed my mind and I think Lee's going to win," said Cowell during a Tuesday appearance on The Ellen DeGeneres Show.
"But the last two years I've gotten it completely and utterly wrong. So I don't think anyone's listening to me anymore. But it's just a hunch."
Cowell said there's just something about Dewyze's background that makes him feel like the 23-year-old from Mount Prospect, IL has what it takes to win.
"There's something about him," Cowell told DeGeneres, his fellow American Idol judge.
"The fact that he's worked in a paint shop, he's talented, he hasn't had any real breaks in his life. This has given him a shot, so I like that."
This week's American Idol finale will also mark the end of Cowell's time on the show's judging panel, as he's leaving to instead launch an American version of his British The X Factor reality series for Fox in Fall 2011.
When asked by DeGeneres if he's happy or sad to be saying goodbye toAmerican Idol, Cowell said it's a "combination of the two."
"I am feeling a bit sad because we're nearly there," he explained.
"But at the same time, do you remember those last three weeks when you were leaving school and you couldn't wait to get out? It's a little bit like that. It's kind of exciting. I'm not being ungreatful. I've had a fantastic time. The show changed my life. I just kind of knew it was time to do something different."
"Have you been in an extra-good mood because you knew you're leaving?" asked DeGeneres.
"I haven't thought about it like that," answered Cowell with a laugh.
"I don't know, I just felt a little bit happier. Maybe it's that. When you're in this position, you start remembering all the really great times you had. We've had a blast over the years."
Cowell announced he was leaving American Idol on the same January day the show began taping the Hollywood Week round in which DeGeneres joined the judging panel, and he expressed regret for the fact that the announcement overshadowed her addition.
"I do actually feel guilty about that. I genuinely do," he told her.
"I didn't think about that, which is it's your first day and two hours before you're starting I held a press conference and said, 'Oh by the way, I'm leaving.' Nice way for you to start. But that was Fox's idea, not mine."
American Idol's final ninth-season performance episode will air live tonight at 8PM ET/PT before the winner is crowned at the conclusion of Wednesday night's live 127-minute results show, which begins at 8PM ET/PT.