NEW YORK - Conservative commentator Glenn Beck is leaving CNN Headline News for Fox News Channel, where he will host a weekday show at 5 p.m. starting next spring.

Beck will also do a weekend show. His daily radio show is heard by nearly 7 million people, ranking him fifth in popularity behind Rush Limbaugh, Sean Hannity, Michael Savage and Laura Schlessinger, according to Talkers magazine.

He sensed growth opportunities at Fox, which appeals to a more conservative audience and has many more viewers than CNN Headline News. Although he won't be in prime time, he gives Fox some bench strength in case there are any changes to its strong prime-time lineup.

Beck said he was trying to improve as a TV host and that he appreciated the chance to have Fox News chief Roger Ailes as a mentor.

"Roger felt that I had a real good sense and gut for what the average person in America is feeling and I think that needs to be reflected on television," Beck said.

He said he wasn't sure how his talk show would be different on Fox. He's also unclear how long he will remain on CNN Headline News' schedule now that he's a lame duck.

Fox currently has a political show with rotating hosts at 5 p.m. The network is also due to lose the host for its 6 p.m. newscast, Brit Hume, who is taking on a part-time role after the election. Fox hasn't said who will fill Hume's time slot.

Beck's departure is a blow for CNN Headline News, which first broke its continuous, half-hour newscast format in 2006 by starting Beck's show. It was an instant sensation, and led the network to launch another talk show with Nancy Grace, which now outrates Beck.

"I was such an island over at Headline News," Beck said. "I had to bring my own audience, where I think there are a lot of people tuning in for comment on the day over at Fox."

Beck's CNN Headline News show airs at 7 p.m. EDT and is repeated at 9 p.m. The network is about to replace the 9 p.m. rerun with a rerun of Lou Dobbs' CNN show, but Beck said that had nothing to do with his decision to leave.

"Glenn has been a terrific employee and colleague to many of us at CNN," said spokeswoman Janine Iamunno. "We wish him well."