James Garner is an awfully agile moseyer, but moseying is a virtually lost art, and "Bret Maverick," despite Garner's bolstering presence, marches to a drummer who's both tired and dated. The only-nominally-new NBC western series premieres as a two-hour movie tonight at 9 on Channel 4, and it takes just too great an effort to like it very much.

"Hey, it's him! It's him!" shouts a little boy as Garner rides into Sweetwater, Ariz., with his back to the camera. But celebrity can be a mixed blessing. "Don't do that!" he scowls at a young woman photographer about to snap his picture (it's Darleen Carr and not, unfortunately, Mariette Hartley). Too late -- the flash frightens his horse, and Maverick falls mortifyingly off with a thunk.

Soon he's standing up to prudes and jackanapes like in the good old days. "Some people have no shame," huffs a biddy. "And others have enough for everybody," Maverick retorts.

Garner has not played Maverick on television in 20 years, since he left the original and overrated Warner Bros. series on ABC. The episodes that starred Jack Kelly and, later, Roger Moore, were never as good as Garner's, because his laconic grin and seasoned exasperation made the scripts and situations seem funnier than they were. He's more seasoned than ever, but tonight's script, by Gordon Dawson, really is beyond repair, and the venture seems so intrinsically anachronistic you can almost see the vultures circling.

It includes an arduous outing in the second half, with Garner and his old "Rockford Files" crony Stuart Margolin (also the director) wandering around some of the mangiest countryside ever photographed for TV. The manginess is all right; it brings to mind the amusingly squalid neighborhoods that Garner's Jim Rockford used to frequent. But Margolin -- as a n'er-do-well named Philo Sandine who fancies himself to be an Indian called Standing Bear -- isn't so much funny as annoying, and the sequence sums up the essential aimlessness of the whole enterprise.

"Maverick didn't come here to lose," Garner sings in the closing title tune, but Maverick doesn't stand much chance of winning, either.