Montgomery County: Key to Obama-McCain battle. Get ready for the ultimate political barrage.

In the back of the Beverly Hilton International Ballroom, CNN Magic Wall manipulator John King was jiggering yesterday with a facsimile of his network's compu-screen that can seemingly identify every single voter in the United States:

United States. Pennsylvania. Philadelphia Region. Montgomery County.

Up popped the Kerry-Bush results from 2004.

"If Barack Obama can match these numbers, he'll be the next president," King said.

So the entire election hinges on Montgomery County?

No, said King. But if Obama wins there, by a good margin, he'll be winning similarly in other key suburbs in St. Louis and in Ohio, and that could tilt the electoral balance.

Conversely, if John McCain can keep Obama's victory margin thin in those areas, King said, he should prevail.

Elvis Costello: Talking music. After his way-decent performance filling in for Dave Letterman a few years back, Elvis Costello will come to Sundance Channel in December with what sounds like a truly fascinating show, Spectacle: Elvis Costello With . . .

Already in the can are performances and interviews with Elton John (who's a co-producer), former President Bill Clinton, artist-director Julian Schnabel, and rock legend Lou Reed. Promised for some of the other nine episodes are younger and more female artists and musicians.

The man born Declan MacManus said he chose his stage name because Elvis Presley was already taken. "We just moved on down through the family names until I arrived at Costello, which is a family name," explained.

Costello declined to say what new artists he's listening to, "not because I can't recall their names, but because then they don't necessarily want my stamp of approval. That might kind of make them unhip."

Right.

One of Costello's best experiences so far doing the show: getting the notoriously reticent Lou Reed to open up: "He actually told a joke," Costello marveled.

"Deadwood" still dead. It's an annual event. Critics, bugged by passionate readers, ask HBO honchos about the odds on a Deadwood movie finale.

"Slim and none," says HBO copresident Richard Plepler, who's looking more and more like former HBO boss Chris Albrecht every day.

Having failed with John From Cincinnati (even actress Chandra West, who played porn-star mom Tina Blake, said the other day she had no idea what was going on), Deadwood creator and executive producer David Milch is hard at work on a new police series, Plepler said.

Last of the Ninth, about New York cops in the 1970s, brings Milch back to the realm of his Hill Street Blues and NYPD Blue successes. No start date for the series, which Milch is cowriting with Blue collaborator and former NYPD cop Bill Clark.

West, like almost everybody who has worked with the brilliant, and eccentric, Milch, raved about the John creator: "It was absolutely a totally unique experience, unlike anything I've ever done before," she said. "So, it was incredibly fun and interesting and challenging and everything you might think working with someone like David would be."

So confusing, too.