LOS ANGELES

CBS research chief David Poltrack said yesterday that if "Crazy Like a Fox," which has just been moved by the network to Wednesday night at 9, beats out NBC's new "Blacke's Magic" in that time slot . . . and if the new "CBS Sunday Night Movie" beats NBC's Sunday night movie . . . and if one of CBS' upcoming mini-series turns out to be a blockbuster -- CBS could still win the primetime ratings crown this year . . .

He said the NBC Sunday night movie, which has been averaging an 18.6 Nielsen rating and a 28 percent audience share so far this year, is particularly vulnerable because CBS will have a 10-point ratings lead from "60 Minutes" and "Murder, She Wrote" going in with its new movie series that night.

Poltrack said, "I'm not going to tell you that we will win but I'm telling you how we can win from now till the end of the season." He said it was the movies that have given NBC its leadership this year so far.

CBS Entertainment President B. Donald (Bud) Grant opened up his network's share of the winter TV press tour Tuesday night by once again displaying his special skills in handling the trade press . . .

He doesn't answer their questions . . .

Instead, moving among the dinner tables at Jimmy's with a microphone in his hand, just like Phil Donahue, Grant entertained . . . but seldom illuminated . . .

Skipping through Captain Airwaves' notebook (Airwaves, were you writing with your toes again?) Grant:

Would not reveal what the B. in his name stands for. "Some smart ass said it stood for Brandon the first name shared by the programming competition at both ABC and NBC but we'll go with Bill" . . .

Has the financial squeeze at CBS since the aborted Turner takeover caused Entertainment any trouble?

"Our development budget -- which is based on need -- is the highest ever" . . .

How long will he stick with "Mary" on Wednesday nights?

" 'Stir Crazy' was doing 15, 16 shares in that time slot and now 'Mary' is doing 24, 25. If it continues to be as good as it is and as long as Mary Tyler Moore wants to do it," CBS will continue. He said it could be moved from its current time slot, however . . . Ditto "Magnum, P.I." . . .

Grant said that the nighttime serial form has probably "slipped" in popularity. "The serial has peaked but all good things must come to an end" . . .

He said "Dallas" is "doing pretty good," although it's down four share points this season; "Knots Landing" is doing "great"; and "Falcon Crest" is down four points too but that could be blamed on its "Dallas" lead-in.

Grant said CBS is working on a deal with James Garner for a half-hour sitcom in the fall but they haven't even come up with a "concept" for the series yet . . .

It won't be a rip-off of Garner's "Murphy's Romance" film because the sitcom project is in another studio . . .

He admitted that the network is still having trouble coming up with good series at the crucial 8 p.m. time slot . . .

Grant thinks "Twilight Zone" is a "terrific show" but wouldn't promise that it will be back next fall . . .

He pointed out that the 16.9 primetime Nielsen rating for CBS so far this year was the same rating that won the season for the network in 1984-85 . . . "There's been quite an audience shift from ABC to NBC," but "I think our audiences have improved in certain key demographics" . . .

Grant said CBS has four shows ready to go later this season, including a one-hour drama series "Bridges to Cross," starring Suzanne Pleshette; the sitcom "Tough Cookies," with Robby Benson as a cop; "Fast Times at Ridgemont High," with Ray Walston; and a sitcom featuring Harvey Korman and Valerie Perrine adapted from a skit on the "George Burns Comedy Week" series . . .

He said CBS would also like to produce more late night shows like "Night Heat" . . .

As for "West 57th," Grant said "we'll know soon" when that CBS News magazine returns to the air . . . but wouldn't make a guess as to when and what time period it'll get . . .

Grant said "Death of a Salesman" will also be repeated and "a lot faster than we normally would" because it was so "brilliant" . . .

As for the return of "Mike Hammer" it appears that unless the upcoming two-hour movie "delivers great numbers," don't expect it back as a series in the fall . . .

"Trapper John, M.D." is gonzo for good . . . after this season . . .

Responding to ABC Entertainment President Brandon Stoddard's admission that primetime TV is often boring and dumb . . . Grant said, "I hope our programs are never dumb.

"We're in a results business: Our performance is the only thing that we can measure" . . .

But Brandon "stood up tall," Grant said of Stoddard, who is probably the tiniest executive in TV . . . adding, "that was a cheap shot."

And Finally

Josh Mankiewicz, who has been at the Atlanta bureau of ABC News in recent months, leaves the network to join WCBS, the CBS flagship station in New York Feb. 17 . . .

Mankiewicz, whose father is Washington public relations executive Frank Mankiewicz, was a reporter for Channel 7 in Washington before moving to ABC . . .