When Mariah Carey walks out on your new TV show, just four days before she's scheduled to be the main attraction on its debut broadcast, you do the best you can to find a fill-in. Which is just what the folks over at CBS's "Early Show" did Friday.

Who did they come up with?

The president of the United States.

Bryant Gumbel was on his way down to Washington over the weekend to interview President Clinton for today's premiere broadcast of Gumbel's show, sources say.

CBS News reps wouldn't talk about any last-minute bookings; Senior Executive Producer Steve Friedman meant what he said when he told The TV Column last week that the show's been reclassified as top secret.

Carey threw over CBS and got herself booked on NBC's competing "Today" show when CBS didn't produce the necessary permits for her planned outdoor mini-concert on "Early Show" by the end of the workday Wednesday.

Clinton's appearance leads off a week-long string of planned "Early Show" interviews with presidential hopefuls, including Texas Gov. George W. Bush tomorrow, Vice President Gore on Wednesday and Bill Bradley on Thursday, according to a program listings guide sent out before "Early Show" became "Top Secret."

Ratings desperation prevailed over Fox censors this past weekend when the network reran the "Home" episode of "The X-Files"--an episode so icky it was banned from the network's air for three years.

Until yesterday, "Home" had run just once on the broadcast network, back in 1996 when "The X-Files" was in its fourth season. In the episode, agents Scully and Mulder investigate a case of infanticide in the little town of Home, Pa., where the body of a malformed baby has been uncovered. This leads them to the Peacocks, a clan straight out of "Deliverance." Its sole members are three men who are mating with their own mother in order to grow the family tree. Did I mention that Mom has no limbs?

Fox got lots of mail on this one--some about the brothers having sex with their mutilated mother; some about the hideously malformed newborn buried in a shallow grave. But what made people really crazy was the scene showing the bloody beating death of the town's Sheriff Andy Taylor. Yes, the same name by which Andy Griffith is well known, thanks to the eight years he spent playing the beloved sheriff of the little town of Mayberry, N.C., on "The Andy Griffith Show"--better known in syndication as "Andy of Mayberry."

And, there were the advertisers. Advertisers who buy time on "The X-Files" know they're in a show that can be pretty grisly, and they're okay with that. But "Home" made them stop and think, and the episode would've been a tough sell if Fox reran it. So, the network decided to turn lemon into lemonade and "ban" it after the fact.

And "banned" it stayed--until two things happened.

First, Fox's cousin cable network fx--both are owned by Rupert Murdoch's NewsCorp.--held a poll last year asking fans of "The X-Files" which episode they'd most like to see again. Guess which one won, hands down?

Second, Fox went into a ratings meltdown this season, with its new crop of series withering across the prime-time landscape. That included the DOA debut of "X-Files" creator Chris Carter's sci-fi drama "Harsh Realm." Carter was livid when the plug was pulled, blaming Fox for botching the show's launch.

These days, securing another season of "The X-Files" is looking even more important to the suits at Fox--as is keeping its ratings up so it's worth returning. Not to mention keeping Carter happy so those negotiations go smoothly. To accomplish all of the above, the Fox guys figured that the final rerun broadcast before the series' season debut next Sunday had better really make some ratings news.

Hence, "Home."

Llewellyn Wells, producer of "The West Wing," was preaching to the converted during a recent visit to George Washington University in what he described as a "grass-roots" effort to lure more younger viewers to his new NBC White House drama series.

But the hundred or so students in attendance had already been lured, judging by their reaction to an airing of an upcoming episode and the softball questions lobbed to Wells and cast members Bradley Whitford and Dule Hill. No critics here.

"I'm a die-hard fan," said GW junior Mike Plostock. "It adds excitement to being here."

Wells said the session, held in a makeshift viewing room between the school bowling alley and a noisy pool hall, was the first in what he hopes will be a country-wide campus tour. And it's all in the name of improving the show's ratings among young viewers.

The show now ranks first in its Wednesday night time slot, but among the younger viewers that NBC covets, "West Wing" falls behind two ABC sitcoms.

"It's not something young audiences immediately are attracted to," Wells told The Washington Post's John Maynard. "Once we get them to watch it, we think they'll stay as viewers and get caught up in it."

Whitford, who portrays Deputy Chief of Staff Josh Lyman, assured his adoring fans that the show should be just as popular with the younger crowd as with older, more politically minded folks.

Questions ranged from how much actual shooting the show did in Washington, to what it's like to work with Martin Sheen, who portrays the commander in chief.

"He has so much wisdom," offered Hill, who portrays presidential aide Charlie Young. "At the same time, he's very laid-back and cool."

One fan veered off course and asked Whitford about his role in "Billy Madison"--a college fave starring Adam Sandler. "I have never seen an inch of that movie," Whitford confessed. "My wife and I were trying to have babies and we needed the money."

The "West Wing" crew was in town over the weekend to shoot exterior scenes at the Korean War Memorial, the Supreme Court and Arlington National Cemetery.

One exterior shot shown during Friday's screening drew a reverent hush from the GW crowd--Georgetown Station, an M Street bar frequented by GW students.

CAPTION: President Clinton is expected to be among this morning's guests on the premiere of Bryant Gumbel's "Early Show" on CBS.