What is prime time, anyway?

That’s a discussion prompted by recent news out of Fox News. The Drudge Report on Thursday signaled that Fox News host Megyn Kelly — currently on maternity leave — will move into the 9 p.m. daily prime time spot now occupied by Fox News stalwart Sean Hannity, who pronounced himself “happy” with the change.

TV news commentators have been wondering just how the network will pack all of their prime-time talent into prime time. After all, Fox News has signed long-term deals with Bill O’Reilly (8 p.m.), Hannity and Greta Van Susteren (10 p.m.), among others. From where does the square footage for another star come?

Mediaite’s Noah Rothman, in a Current TV segment Thursday, advanced a resolution: “Seven p.m. is a prime-time hour. You can give 7 p.m. to prime-time hosts and keep all your lineup safe.” Really? Sounds like a question for Robert Thompson, a Syracuse University TV and pop culture professor who notes: “In the old world of network broadcasting, prime time was 8 to 11 Monday through Saturday, and on Sunday, 7 to 11.” In cable, however, it can be 7 to 11 p.m., or even 6 to 11 p.m. on any day, says Thompson.

More hours translate into more space for all those cable news egos. Will Hannity move to 7 p.m.? Will there be some crazy co-anchoring scheme? What about 7 p.m. slot-holder Shepard Smith? Already Fox News chief Roger Ailes announced, at a conference, that he’s exploring with Smith a “new way to deliver news.

This whole scheduling thing constitutes a very, very good problem for Fox News. Ailes has the enviable task of finding slots for a wealth of talented broadcasters with proven records of attracting viewers. The night just isn’t long enough for Fox News.

Just what prompted Kelly’s 9 p.m. berth is murky. Fox News’ PR shop, for starters, hasn’t even officially confirmed the story. A Fox News spokesperson e-mailed: “We will neither confirm nor deny any programming schedule changes. As previously stated, the network has signed long-term deals with Megyn Kelly, Bret Baier, Shepard Smith, Bill O’Reilly, Sean Hannity and Greta Van Susteren.”

Yet Kelly’s elevation from the afternoon show “America Live,” which airs between 1 and 3 p.m., to a prime-time spot has been a consensus inevitability for some time now. Kelly has gotten good ratings — she finished last year as the 10th cable news show, despite her early-afternoon slot. Kelly has flashed the requisite Fox News anchor’s scorn for liberalism, which is de rigueur for advancement at the network. Kelly has a strong on-air presence that manages assertiveness sans arrogance; when she occasionally stammers in her delivery, she recovers as well as anyone in television. Kelly is expert in getting the guests in her “fair-and-balanced” interviews — always a sham, of course — to go after one another. Kelly has often prompted the Erik Wemple Blog to comment to our officemate, “She’s very good, isn’t she?” Officemate generally agrees.

On the other hand, Kelly said the Washington Monument was tilting after the August 2011 earthquake. Not to mention that she repeatedly shilled for a novel titled “The Ghosts of Manhattan.” Author: Douglas Brunt, her husband. Somehow the conflict of interest escaped the attention of the Fox News public editor.*

The world of cable news, however, is driven not by media critics’ self-important quibbles, not by contacts, not by intangibles, not even by looks. It’s driven by ratings, and they may explain why Kelly is moving into prime time. In the first quarter of 2013, Fox News’ prime-time ratings saw a 34 percent drop in the 25-54 demographic, a key audience when it comes to hooking advertisers. The drop was exaggerated, no doubt, by the robust 2012 audience for presidential primary coverage, but look: Fox News’ prime-time viewership among that younger demographic is on a five-year skid. Ailes, often alleged to be a paranoid type, may well be guessing that the 42-year-old Kelly will pull in the youngsters more effectively than the 51-year-old Hannity.

A message of caution from Thompson, the Syracuse University professor: “If they think that Megyn Kelly is going to bring a bunch of my college students to Fox News, they’ve got another thing coming.” That said, Thompson says Kelly could improve performance among some younger viewers as well as among women.

A more consequential question is whether Kelly will appeal to the red-meat conservatives who’ve been tuning into “Hannity” for as long as memory serves. The Erik Wemple Blog’s guess is: Hell no. For corroboration on this front, we turn to Joe Muto, the famed “Fox Mole” who wrote the book “An Atheist in the Fox Hole: A Liberal’s Eight-Year Odyssey Inside the Heart of the Right-Wing Media.” In Muto’s travels at Fox News, he absorbed a great deal of workplace atmospherics, including these observations:

[A] few years after I worked with her, [Kelly] was imported to New York for good and was given a two-hour daytime block, for which she adopted a highly aggressive, archconservative persona. My first thought on seeing her in action was, She’s faking it. And my second thought was, She’s a genius. Creating a new persona for herself was somewhat cynical but was overall a brilliant career move. She was smart, talented, and beautiful, but that would only get you so far at Fox — Ailes wanted to see a point of view as well. So Megyn started to act a little less smart and a lot more Republican when she was on air, and suddenly there was chatter in the hallways that she was in the running for Greta Van Susteren’s prime-time slot.

Those who watched Fox News’ daytime programming could see the same dynamic that Muto had espied from inside the tent. In her day-to-day work on “America Live,” Kelly swallowed the Fox News story planning, which tends to go heavy on any pieces that cast the Obama White House in a negative light — Benghazi, spiking health-care costs, etc. And in moderating on-air discussions, she was always careful to place her thumb on the right side of the scale. There was always something suspect about the presentation, something that left the Erik Wemple Blog asking, Does this individual actually believe these things?

The moment that Kelly’s program tilts at women’s issues, the alienation of the old “Hannity” crowd should be upon us. After all, Kelly profiles as a genuine feminist on such matters, despite her unconvincing protestations to the contrary.

Should Kelly move to the extreme right in her prime-time persona, she’d be doing a tremendous service to the Fox News brand. For years now, Fox Newsers have answered attacks that the network is a Republican Party organ by arguing that its daytime programming (9 a.m. to 4 p.m., at least) is objective stuff. Straight up the middle. That’s the central, animating deception of Fox News, one that allows its defenders to suggest that the news/editorial split is quite the same as that of any newspaper in the land. So: If  on her new show Kelly evinces an even harder-core brand of conservatism, she’d add credence to the notion that her work as a daytime anchor was tilt- and opinion-free. Fox News is such a blast.

To recap: Megyn Kelly could be ascending to Hannity’s spot because she was smart enough to bargain for the promotion in her last contract negotiations; or because if she didn’t get it, she would have fled to one of the networks that were eager to sign her; or because she could attract different viewers to Fox News’ prime-time lineup; or because she’s just plain good at her job. At the same time, it’s quite clear what didn’t actuate Kelly’s promotion: Hannity’s reckless tendency to latch on to the latest flimsy, factually challenged anti-Obama conspiracy theory. Had that been a problem for Fox News brass, this switcheroo would have taken place a while ago.