Grant's 1995 appearance on NBC's "Tonight" show after a prostitution arrest, where Lenofamously asked "what were you thinking?," was seen in retrospect as a turning point in thelate-night race. It drew a huge audience and propelled Leno to the top of the ratings, a spot hewould not relinquish.
Letterman did not court last week's battle with Palin, who called him "perverted" for making ajoke about her daughter getting "knocked up" by New York Yankee Alex Rodriguez, and he saidin retrospect the remark was in poor taste.
Palin rebuffed his invitations to appear on the show, but that might not matter. The story hadthe effect of turning the attention to Letterman at a critical time, during the second week of hisnew competition with Leno's replacement, Conan O'Brien.
"It will be interesting to see if that can be maintained or whether it is one of those temporarythings," said Robert Thompson, director of the Center for the Study of Popular Television atSyracuse University.
The final numbers won't be out until later in the week, but there's a strong chance thatLetterman could average more viewers than the "Tonight" show in the second week of O'Brien'snew 11:35 p.m. job. That hasn't happened since 2005, and the timing is significant: some of Leno'sold fans may be more amenable to searching for a new late-night habit during the transitionperiod.
It's difficult to tell whether Letterman received a boost this week because of people interestedin what he was going to say about Palin. Strong guests like Julia Roberts and DenzelWashington were a boost, too.
Letterman has referenced the NBC transition in a handful of jokes over the past two weeks,many of them poking fun of himself as much as his rival.
"Conan O'Brien, of course, is the new host of the 'Tonight' show,"' Letterman said a week ago."Did they even look at my audition tape?" On a top 10 list of Signs it's Time for Kim Jong-Il toretire, was No. 2: "Republic already named his successor, Conan Jong-Il.
Topping the list of Surprising Facts about Sonia Sotomayor was: "Demonstrated impeccablejudgment by watching Conan." Despite the competition, no doubt it's hard for Letterman toexhibit the same animosity toward O'Brien as he did toward Leno.
O'Brien has openly acknowledged his debt to Letterman, and his subversive anti-talk showstyle is more reminiscent of what Letterman did in the 1980s than what Letterman is doingtoday.
Letterman maintains his biting sarcasm, but at age 62 he has evolved into more of a traditionaltalk show host than his rivals.
Thompson said he believes Letterman is more topical than ever, in part a recognition of JonStewart's success at Comedy Central. The Letterman of two decades ago attracted attention fordropping watermelons from the roof of a building or wearing a Velcro suit; now he gets it forcharged interviews with John McCain or Joaquin Phoenix.
When Letterman did a brief filmed skit last week tied to Washington's new movie, "The Takingof Pelham 1 2 3" it seemed like a quaint throwback; O'Brien does such pre-filmed segments allthe time.
"David Letterman's biggest problem is he was brilliant in going against the grain," he said."David Letterman is now the grain.
He's his own toughest act to follow. So that's why it is smart that he has tried to change thegame." Letterman, who went through a life-changing heart surgery and became a father in thepast decade, seems committed to the new competition. It was revealed this week that he hadagreed to a contract extension that will keep him on the "Late Show" into 2012, and there's noindication that he's looking toward retirement.
His longevity, however, may be his biggest handicap in getting back to the top.
"By and large, late-night comedy is a young wise-guy's business," Thompson said.
The fans who thought he was fabulously hip in the 1980s now have their own teen-agerslooking to make their own late-night TV habits. Letterman has a love-him-or-hate himpersonality, and a transition by one of his competitors isn't likely to change the minds of viewerswho made them up years ago. He jokes about all politicians but it's becoming clearer where hissympathies lie -- something that Palin and her supporters sensed in their criticisms.
NBC has touted O'Brien's show as the fun place to be in late-night, particularly for youngerviewers, with the implication that Letterman is a cranky old man.
It would be foolish to count him out.
Palin may have inadvertently given Letterman a platform at a time when it is most valuable;the next few weeks will show how he's been able to use it.