Everything ain't all gum and root beer, sister!'' growled David Letterman to his audience on a recent evening. Well, it was a mock growl, of course, but that almost goes without saying everything Letterman does is tinged with mockery, suffused with the cool green glow of bile. A certain comic asperity and genuine grumpiness are what help make Dave Dave.
And right now, we're getting the Daviest Dave possible: The current run of Late Show with David Letterman is Letterman working at near-peak form. Why? Because the host is in a bit of trouble, and Letterman always responds well wittily, goofily, belligerently to trouble. Over the past year, he's watched The Tonight Show become a regular ratings challenge that, lately, can actually beat him. He's been hobbled by the fact that CBS has turned into an arid prime-time desert that provides few strong lead-ins to Late Show.
We've seen Letterman through his rough patches before. It brings out the best in him which is to say, he lets down his stoic guard and starts winging it. These days, his show has a looseness that makes for a zippy, unpredictable hour. I liked it when he told a joke that bombed and then, as if the wind had been knocked out of him, he lay down on the stage, ''for a breather.'' I liked it when, announcing that the following night's guest would be Julianna Margulies from ER, he willfully misidentified the NBC smash as a CBS show and described ER as being ''so authentic, every time I watch it, I get sick.''
To be sure, Late Show's choice of guests continues to be exceedingly peculiar Kevin Costner, sure; Brooke Shields, fine; but Jerry Van Dyke?
In the evening's leadoff position? Letterman's bookers are practically daring half his audience not to switch over to The Tonight Show for two segments or so.
But the Late Show interviews themselves are just dandy that lame rap about his being mean to guests is sooo tired. Letterman was particularly charming with My So-Called Life's Claire Danes, mostly because he was so charmed by her. In the company of the 16-year-old actress, he reverted to his aggressive-paternal mode, asking about her 18-year-old boyfriend: ''Is he a nice guy, or is he a punk? I'll bet he's a punk. Is he going to finish college?''
It used to be that what annoyed viewers about Letterman was that he seemed aloof, too hipper-than-thou. Now that he's more civil to guests and critical of himself, people are saying he's uncool: Need I do more than remind you that this very magazine declared him ''Cold'' in our ''Cool Issue'' this summer? One of the axioms of cool is the appearance of serene, no-sweat disinterestedness. For a long time, that sort of pose jibed with Dave's Midwestern reserve. But Letterman's gotten better-more unpredictable, more than a joke machine in a suit-as time's gone on, in no small part because he no longer has any use for surface coolness and emotionally empty irony.
Letterman's outward anxiety and exasperation with himself are what distinguish him from his hero, Johnny Carson; he's fashioned a durable persona as the genial goofball who becomes nettled and furious in the space of a second. If the notion that life ain't all gum and root beer disturbs you, go watch something else. A-