It's easily the most-anticipated vice presidential face-off ever. ¶ When Sarah Palin and Joe Biden meet in St. Louis tonight for their only debate, both will be trying to win over -- as Palin put it -- the "normal Joe six-pack American." ¶ While the focus will be on Palin more than on Biden, both have a lot to prove. Biden, the senator, former presidential candidate and foreign policy expert, cannot be seen to wield his experience to patronize her, and Palin, who has stumbled in interviews with non-responses, must sound like she knows what she is talking about. For Palin, the debate gives her a chance to overcome the doubts in a 90-minute showcase, the first time that most Americans outside Alaska will see her in a lengthy give-and-take session. But a poor performance could cement a negative image for the rest of the campaign. But don't discount her: She shined in 23 debates in her victorious march to become governor.

Biden, who remains the all-but-forgotten man of the campaign, will be out to prove that he is an asset to the Democratic ticket -- by demonstrating command of the issues, attacking Republican presidential candidate John McCain and not Palin, and keeping his brain ahead of his sometimes too-quick mouth.

The bottom line: Palin must know her facts. Biden must know when to stop.

The format could help protect the candidates from themselves, forcing them to keep answers short. Moderator Gwen Ifill of PBS will ask the questions, which can be about any topic. Each candidate will have 90 seconds to respond with a two-minute conversation to follow.

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What to look for tonight

Whether you're watching the debate on TV, online or catching the highlights on YouTube, here are some tips on what to look for:

DON'T PLAY THE EXPECTATIONS GAME

Pundits and campaign managers manipulate perceptions so it's easier to later declare their candidate the winner. All week, Republicans have been praising Joseph Biden as a wonderful statesman to raise the bar for him while Democrats have been unearthing videos of Sarah Palin's Alaska debates to prove she's no pushover. In the basest analysis, if Palin sticks to her message without giving Tina Fey too much material for the next "Saturday Night Live" skit, she will have succeeded. If Biden curbs his spontaneity and avoids badgering Palin, he will have succeeded.

TAKE 'EXPERTS' ADVICE' SPARINGLY

They are all over the map anyhow: Be nice. Go for the jugular. Be yourself. Pretend she is a man. Give him four Percocet. Don't look like you memorized the index cards.

There's even a website compiling much of the advice, www.presidentialdebateblog.com.

"If I were advising Palin, I'd tell her, 'Don't answer the question you were asked, answer the question you wish you were asked, with generalities,'" said former Yale University debater and now law student Aaron Zelinsky, founder of that website. And for Biden: "Avoid the Percocets [the popular painkiller]. I don't think people want a sedated VP. He should act himself and focus the firepower on McCain."

WATCH THOSE GENDER POLITICS

Will Biden be an attack dog or a puppy dog? Will Palin condemn her rival for "a patronizing attitude," as Democrat Geraldine Ferraro did of 1984 debate rival Republican George H.W. Bush? Don't count on it.

Despite Palin's questionable command of the issues in her few interviews to date, in some ways, the stakes are higher for Biden, whose challenge is to strike a tone neither too condescending nor too deferential. His mock debate rival has been Michigan Gov. Jennifer Granholm, and he has called Sens. Hillary Rodham Clinton and Barbara Boxer of California for advice on debating a woman.

"If a male patronizes another male, that's seen as just part of the game," said Janet Flammang, chairwoman of Santa Clara University's Political Science Department, who studies gender politics. But, she said, the reaction is generally much more negative if a man seems condescending to a woman in such a setting.

The best advice for Biden, said Shanto Iyengar, professor of communications and political science at Stanford University, is "just let her express herself."

BEWARE OF MULTITASKING

You can catch the debate on all of the major broadcast TV stations, several cable TV news stations and streaming live on numerous websites. But technology is changing how we view debates, making it easier to miss the big picture. Many websites invite viewers to join online chat forums as the debate unfolds. Current TV wants viewers to Twitter responses, some of which then show up on the debate broadcast. CNN offers its high-definition viewers' an instant live-audience response as the debaters go at it. But if you can watch, think, type and respond to the viewer who disagrees with you all at the same time, give it a try.

BE CAREFUL HOW YOU PICK WINNER

Some of the most memorable lines in vice presidential debates have been uttered by the losing team. Ferraro's condemnation of a "patronizing" Bush in 1984, and Lloyd Bentsen's devastating 1988 putdown after Dan Quayle compared his inexperience to John F. Kennedy: "Senator, you are no Jack Kennedy." Of course, it was Quayle who went on to the White House.

And, what is winning anyway? Often, says, Mark Petracca, chairman of the University of California at Irvine's Political Science Department, "You've succeeded if you've escaped humiliation or a rhetorical blunder."

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