The broadcast networks are trying to pick off each other's newsmagazines this summer.

First, CBS decides to air a summer edition of "48 Hours" on Monday, opposite NBC's "Dateline." "48 Hours: Monday Mysteries" attracted a boffo 14 million viewers last week. Granted, "Dateline" didn't air that night; it was preempted for National Basketball Association coverage.

Quicker than you can say "why didn't we think of that," ABC announces a short-flight newsmagazine called "Vanished," about unsolved missing-persons cases, which will air Thursdays at 10 p.m.--opposite CBS's original "48 Hours." "Vanished" debuts tonight. And when "Vanished" vanishes, ABC will trot out "Nightline in Primetime: Brave New World" in the Thursday time slot also occupied by "48 Hours."

Then, after seeing its boffo numbers for Monday's "48 Hours," CBS announces yet another edition, called "48 Hours: Tuesday Adventures," airing opposite "Dateline" at 10 p.m. starting July 6.

What gives?

The networks have discovered that in the summer, news works. Last summer, newsmagazines, even those that were largely rerun packages, dominated the broadcast TV Top 20 rankings. The advantage of news is that the producers can freshen old material with an update. It's hard to do that with a sitcom, observes "48 Hours" executive producer Susan Zirinsky.

And "repurposed" news stories are satisfying not only to viewers who didn't catch the report the first time, but also to those who did, Zirinsky says--unlike drama series, which are notoriously weak in reruns.

Viewers find it "incredibly satisfying to have a final chapter" to a story, she says.

But why so much head-to-head competition?

To some degree, this bumping of newsmag against newsmag is inevitable. The prime-time week is so littered with news hours that it's tough to steer clear of them. There are regularly five editions of "Dateline," four of "20/20," two of "60 Minutes" and one of "48 Hours"--for a total of 12 hours of newsmagazines in a prime-time week of 22 hours.

In ABC's case, "Vanished" and "Nightline in Primetime" are warming up the Thursday time slot for the debut of a new "20/20" this fall. CBS, on the other hand, has scheduled entertainment fare on Mondays and Tuesdays at 10 p.m. for fall.

Zirinsky says the scheduling of both "48 Hours" summer programs opposite "Dateline" is a coincidence. "From my perspective, it was not 'Let's go face to face and battle the competition'; it was 'Let's look at our lineup and where we can do some good and where there are places to be filled,' " she said.

Do the summer newsmag wars portend a trend that will carry over to fall schedules? Probably not, forecasts "Dateline" executive producer Neil Shapiro.

"We can all do some reruns and repurposing in the summer, but in the fall there's more pressure to do much more original programming. It may not be so easy to say, 'Can you guys come up with three or four hours here and there?' "

Besides, Shapiro says, it's not good for the genre "because it divides the news audience; therefore, neither newsmagazine gets to prosper."

Retreat!

The Military Channel, which arrived on Washington airwaves just a month ago, ended its over-the-air run last weekend on Arlington's WTMW and local cable systems. It was mustered out in favor of the Panda Shopping Network, a subsidiary of Los Angeles-based TVN Shopping Inc.

Cable industry trade publications have reported that the Military Channel, which specializes in shows about U.S. military history, is facing some serious financial difficulties, though spokesman George Wright maintains it is "sincere in our desire and obligation to fulfill our commitments to our creditors" and hopes to be back on WTMW as soon as possible.

WTMW owner Theodore White told The Post's David Jackson that those reports "played a role" in the switch, "but people seemed to want shopping back on our channel. The Military Channel got a lot of complaints."

Michael Wex, president of TVN, says his outfit is happy to be in the Washington market and that the agreement reached with WTMW, despite the Military Channel's desires, is "long-term." TVN only recently acquired Panda Shopping Network, which offers hefty servings of infomercials and also sells collectibles, especially watches and coins, via both auction and regular call-in formats. Panda is seen in about 20 million households. Wex says he plans to relaunch, rebrand and "upscale" the network toward the end of the year with an emphasis on viewers aged 18 to 34.

It's that time again: The presidential candidates are looking for ways to use the TV press--and the TV press is looking for ways to capitalize on White House candidates.

Fox News Channel has invited each presidential hopeful to co-anchor an edition of "The O'Reilly Factor." For the first half-hour, the candidate would be Bill O'Reilly's sidekick, questioning the day's news makers. The second half-hour would have O'Reilly in the driver's seat, doing an in-depth one-on-one with said candidate.

A Fox News Channel rep says they're doing it "so viewers can get a really good feeling and understanding for what each of the candidates is trying to push."

CNBC wasted no time capitalizing on the exit of CNN's money man Lou Dobbs. Starting Monday, CNBC's "Business Center" is expanding to a full hour, from 6:30 to 7:30 p.m. weeknights, to compete head to head with CNN's "Moneyline News Hour."

New anchors have been named: Ron Insana, currently anchor of "Street Signs," and Sue Herera, who co-anchors "Market Wrap I" and anchors "The Edge."

Current anchor Tyler Mathisen's being shipped over to "Market Watch" at 10 a.m., while Maria Bartiromo will anchor a new weekly program on Fridays at 7 p.m. She'll also anchor the first hour of "Street Signs" at 2 p.m. and will continue to provide reports from the floor of the New York Stock Exchange on "Squawk Box" at 8 a.m. and co-anchor "Market Wrap" at 5 p.m.

The revamped "Business Center" will feature breaking news and more original material from Dow Jones's news properties, including the Wall Street Journal, Barron's and the Dow Jones News Service, the network said.

Meanwhile, "The Edge," currently anchored by Herera, will return to its original format, airing from 6 to 6:30 weeknights, and will be hosted by Bill Griffeth, who also continues to head "Power Lunch" at noon and "Market Wrap" at 4 p.m.

CNBC's "Business Center" has played second fiddle to the Dobbs-hosted "Moneyline" in the ratings, since "BC" debuted in 1997. The cable network's business news senior vice president, Bruno Cohen, said the changes are meant to "capitalize on the recent changes in the financial news arena."

And how is CNN doing Dobbsless?

"The world got along without John F. Kennedy and Jesus Christ. . . . We'll get along without Lou Dobbs," CNN topper Ted Turner is quoted as saying this week at the National Cable Television Association confab in Chicago.

"Profiler" star Ally Walker is bowing out of the NBC drama series to concentrate on her film career, reports the trade paper Variety.

What film career?

This one's a no-brainer for the peacock network. "Profiler" has never been a ratings magnet for the network; last season, it finished 91st out of 168 shows. This season--its fourth--will likely be its last unless NBC, which also produces the show, can do something to interest more viewers in the program. Changing lead actors may accomplish that.

Walker is expected to show up for the first four episodes. And since "Profiler" will debut late in the fall to accommodate NBC's baseball schedule, the network will have plenty of time to contemplate Walker's replacement.

A network rep declined to comment.

CAPTION: Jane Pauley's "Dateline" is being challenged by a new "48 Hours."