After years of being an also-ran in fourth quarter, Fox turned itself around last season to become a threat to the other Big Four networks.

The network is going to leverage those gains this coming season, challenging ABC for No. 1 in the fourth quarter and then going on to win the full season with returning hits like “American Idol” and “24” and several new shows premiering throughout the season that buyers think will do well.

“We’re expecting Fox to have a relatively strong fourth quarter, and by strong I think they could be pushing ABC for 18-49 bragging rights,” says John Spiropoulos, vice president and group research director at MediaVest.

“Fox is starting in a position of strength from last year,” says Sam Armando, senior vice president and director of video research at Starcom.

“And I don’t see a lot of incredible competition right now. I’m not saying the other networks are in bad shape. I just don’t see the programs on the other networks that will pull them ahead.”

Last fall, Fox was up 13 percent in adults 18-49, in part because of hits like “House” and a slew of reality shows, but also because it cut back the number of postseason baseball games it aired, after years of having baseball disrupt its fall schedule. It tied NBC for No. 3, barely behind CBS and only a half rating point behind ABC.

This fall, Fox reworked its lineup to make it competitive virtually every night of the week, and it also has the most-talked-about new show, “Fringe,” from “Lost” creator J. J. Abrams.

Its strongest night will be Tuesday, where it will rank No. 1 with its most-watched scripted show, “House,” and the new "Fringe" in the fall, and then get a further boost when “Idol” returns at midseason.

Fox will be solid on Saturdays against weak competition for the full season with its long-running “Cops” and “America’s Most Wanted,” although ABC will be strong in fourth quarter with college football.

On Mondays, Fox has the returning “Terminator: The Sarah Connor Chronicles” and “Prison Break.” A new drama, “Dollhouse,” about people whose memories are manipulated, is expected to take over for “Prison” in midseason.

Still, ABC will rank No. 1 with “Dancing with the Stars” and CBS will be strong with comedies and “CSI: Miami.”

On Thursdays, Fox will trail the other networks but will be competitive with a reworked lineup of reality shows, including “Hole in the Wall,” a remake of a Japanese game show, and the returning “Kitchen Nightmares.”

On Fridays, Fox will do well with reality shows that viewers are familiar with, including “Are You Smarter Than a 5^th Grader,” which should hold up against CBS’s older-skewing dramas and ABC’s and NBC’s middling unscripted shows.

“What they’re doing to up their weekly average ratings is the reality shows they have on Thursdays and Fridays look much stronger than the Band-Aids they’ve had in the past,” says Spiropoulos. “That will prop them up.”

Fox will be strong on Sundays with animated comedies like “Family Guy” and, later in the season, a spinoff of that show – “The Cleveland Show” – and another new cartoon, “Sit Down, Shut Up” from the creator of Fox’s “Arrested Development,” which is no longer on the air but which has a legion of hardcore fans.

NBC will dominate Sundays in fourth quarter with NFL football.

Fox’s trouble spot in fourth quarter is Wednesdays, when it’ll air the returning “Bones” and “‘Til Death” plus the new sitcom “Do Not Disturb” with Jerry O’Connell.

Fortunately for Fox, the other networks each have some holes on Wednesdays. And Fox will get a huge boost in midseason with the “Idol” results show.

“I don’t think there will be an upset this season,” says Spiropoulos. “Fox has it locked up.”