In the short window of opportunity between last Wednesday's final presidential debate and Nov. 4's Election Day, there are only two arenas for the candidates to visit in hopes of reaching sizable national audiences and winning their votes.

One arena: the prime-time newscasts and Sunday public-affairs shows, where questions will, or should, be tough and unpredictable. The other arena: late-night comedy and talk shows, which are fraught with risks of their own.

Take the three days immediately following the debate, all of which cashed in on the currency of presidential politics.

Thursday night, viewers of CBS's Late Show with David Letterman saw the contrite return of Republican presidential nominee John McCain, who had snubbed Letterman at the last minute and paid the price: days of viciously sarcastic monologues. When McCain did return, it was to get into the good graces of Letterman and his audience. Instead, Letterman peppered him with pointed, intelligent questions about his politics, policies and past. Good for McCain? Not really.

Friday night, Letterman's guests included Tina Fey, who talked about imitating McCain's running mate, Sarah Palin, in ways that were both hilarious and not particularly flattering. Fey likened some of Palin's run-on, meandering sentences as the verbal equivalent of being "lost in a corn maze," and claimed that Palin's Great-Lakes-by-way-of-Fargo accent was an easy and enjoyable one to attempt to imitate.

"Not since Sling Blade," she said to Letterman's delight (and mine), "has there been a voice that anybody could do."

Fey also said listening to Palin made her feel that the Alaskan governor was exactly as smart as Fey herself -- which, Fey added, she suspected wasn't enough. She also not only confirmed that Palin was in talks to appear on Saturday Night Live, but at Palin's own instigation ("She's calling them, I hear," Fey said). Good for Palin? Not really.

And finally, the next night, there was Saturday Night Live itself, on which the Fey and Palin versions of the Alaskan governors shared the same stage -- but so briefly I couldn't even snare a non-blurry screen shot. Eventually, though, they stood at the same podium. Just not at the same time.

The show opened with Fey, once again, as Palin, this time holding her first press conference and listing which states she considered un-American ("New York, New Jersey, Massachusetts, Connecticut, Delaware and California"). The opening skit then cut to backstage at the SNL hallway, where series creator Lorne Michaels and the real Palin were watching a monitor on which Fey was imitating her.

In time, Alec Baldwin walked up, mistaking Palin for his 30 Rock co-star and complaining about Palin ("that horrible woman") until Michaels identified her and introduced them. At that point, Baldwin said to Palin, "You are way hotter in person," and escorted her to the stage, where she took Fey's place -- and finished the skit, in which she refused to take questions even at a bogus press conference. Good for Palin? Hard to say.

She returned during "Weekend Update," ostensibly refusing to go through with a scheduled performance, which Amy Poehler did instead. It was a rap song, with some occasionally devastating lyrics, considering that Palin was the one who was supposed to be singing them. ("When I say 'Obama,' you say 'Ayers'!" she sang.)

And through it all, the cameras cut back to Palin at the "Update" desk, swaying to the music and even raising her hands in a "raise the roof" motion. Good sport? Yes. Good for her image, since she was being ridiculed mere feet away? Perhaps. But good for gaining votes? Again, we'll have to see.

But one vote already is in, and the winner is Saturday Night Live. Early ratings estimated this weekend's audience at close to 14 million, which would be the show's largest draw in 14 years. Back then, it was for the guest host, Nancy Kerrigan, at the height of her absurdly tabloid Olympics duel with Tonya Harding.

This time, it wasn't to watch guest host Josh Brolin, but merely to see an unbilled guest appearance by Sarah Palin. Or the woman who imitates her.

But the key question is this: Of those millions of viewers, what percentage is laughing with Sarah Palin, and what percentage is laughing at her?