Leno leaves 'Tonight' much as he found it

There have been 11 U.S. presidents since 1954 but only four hosts of "The Tonight Show." The latest, Jay Leno, finished his 17-year run Friday night; his last guest was scheduled to be his successor, Conan O'Brien, himself coming off nearly 16 years as the host of the post-"Tonight" "Late Night." Change comes glacially to late-night television: This is a day whose coming was foretold some five years ago, when O'Brien was promised the job, though its most notable upshot -- Leno's intra-network move to NBC prime time -- was a late innovation.

"The Tonight Show" was an American institution when Leno took it over, defined and refined by Johnny Carson over three decades and the model for most of its own competition. The only network job to rival hosting it is anchoring the evening news. If Leno rarely approached his predecessor's heights, if he did not advance or improve or in any significant way re-imagine the brand, he did not destroy it either. He was a caretaker-host and after a slow start against David Letterman's "Late Show" on CBS -- competition created by NBC's decision to give "Tonight" to Leno instead of moving Letterman down from 12:30 -- he pulled ahead in the ratings and maintained the lead.

One's allegiance to Leno or Letterman can be seen as a variation on the old Beatles versus Stones debate: the former safe and mainstream; the latter a little dangerous, working along the unpredictable margins. (It's a glib dichotomy, but useful.) Where Leno sums up an older, more fulsome show-business tradition, Letterman is the godfather to the dry and ironic younger generations of comedy. Drew Barrymore would never have flashed Leno as she did Letterman; Madonna would not have tried her experiment in four-letter words on "The Tonight Show." At the same time, it's hard to imagine Letterman giving Roberto Benigni a ride on his shoulders, as Leno did, or getting into a food fight with Mel Gibson.

Lenoland is a friendly place: friendly for the viewers, friendly for the guests, friendly for the whole apparatus of celebrity self-promotion that such shows both depend on and exist to serve. Leno's "Tonight" was organized as a rousing good time; every show opened with the host glad-handing a clamoring studio audience. (There are moments when you can almost see the applause sign flashing.) While Leno can be serious, and is not without opinions, he made his show a protected place; as a critic, he makes a good straight man. It was to Leno that President Obama went, not to Letterman, for a pulpit from which to sell his stimulus package.