In VP debate, both sides have something to prove

— -- It's rare that the undercard is as eagerly awaited as the title bout. But in this election, the vice presidential debate could be such a matchup.

When Republican Sarah Palin and Democrat Joe Biden face off Thursday night (9 p.m. ET) at Washington University in St. Louis, the 90-minute debate will be the longest — or, perhaps, only — side-by-side look at the two that voters will get before the Nov. 4 election.

Each has plenty to prove to the millions who will be watching. The candidates have to show they could step into the top job if needed. They must excite the party faithful and entice undecided voters. And they must mind the vice presidential credo: "Do no harm" to the nominee, all while sinking their teeth into the opponent.

Palin and Biden each come with their own specific challenges. Since being chosen by GOP nominee John McCain on Aug. 29, the Alaska governor has inspired excitement within the party — especially among conservatives wary of McCain's work with Democrats on immigration and an overhaul of campaign-finance laws. But no one outside of Alaska has seen Palin debate live, and her recent network TV interviews — in which she struggled to answer questions about the government's financial bailout plan and her self-described expertise on Russia — have been widely lampooned.

Palin's credibility has suffered: In a poll out Wednesday from the Pew Research Center, only 37% of Americans said Palin is qualified to be president compared with 63% for Biden. In a Pew poll three weeks ago, 52% said Palin was qualified.

Tonight's wild card: How will Palin handle the intricacies of policy without a teleprompter?

Biden, whose choice as Democrat Barack Obama's running mate was far less of a surprise than Palin's, is known for his windiness, zingers and gaffes.

He muddied the launch of his second presidential bid in February 2007 when he was quoted in the New York Observer referring to Obama as "clean" and "articulate." During a primary debate last year, Biden brought down the house by saying that GOP contender Rudy Giuliani, a former New York mayor, was using just three words in every sentence: "a noun, a verb and 9/11."

The unknown for tonight: Whether the Delaware senator will say something condescending, controversial or clumsy.

"Her vulnerability is sounding as if she's reciting something written on an index card," says political scientist Kathleen Hall Jamieson of the University of Pennsylvania. "You listen to Sen. Biden and you think, he's never seen an index card."

Mitchell McKinney, a University of Missouri-Columbia professor who studies political debates, predicts "an uptick" in viewership from previous vice presidential debates. The first of three Obama-McCain matchups last week drew 52.4 million viewers. "We could be in a situation where we actually for the first time eclipse a presidential debate," he says.

Biden eased off his hectic campaign schedule to spend most of the week prepping for the debate at home in Wilmington, Del., where Michigan's Democratic governor, Jennifer Granholm, played the role of Palin.

Even as both candidates spent most of this week in debate prep, they engaged in the ritual of setting expectations: high for their opponent, low for themselves.

Biden has described Palin as "tough" and "formidable." Palin said Monday that Biden is "a great debater and looks pretty doggone confident, like he's sure he's going to win." In light of Palin's shaky answers on CBS on issues such as the economic crisis and McCain's record on financial regulation — and the resulting criticism even from within her own party — the bar could be lower for her than Biden.

Palin went through more than a dozen debates during her 2006 campaign for governor. To prepare her for tonight, the campaign sent in its top strategist, Steve Schmidt, a veteran of President Bush's re-election campaign, and chief foreign policy adviser, Randy Scheunemann. Prep sessions were moved to the McCain's ranch in Sedona, Ariz., last weekend for the relaxed atmosphere: At least one session was conducted near a creek that meanders through the property.

The strategy is to contrast Palin's "real life, real world results" with Biden's "smooth talking insider rhetoric," said Palin adviser Tucker Eskew. Palin "is eager to share her story, her views — herself — with the American people," Eskew said. "This debate is the latest and the greatest place to do it."

The debate questions, from moderator Gwen Ifill of PBS, will cover topics both foreign and domestic. Viewers, however, should keep these questions in mind:

1. Ready for the big chair?

Biden and Palin didn't get to this debate by winning primary votes; they got picked by the guys who did. They still have to pass the "commander in chief test" with voters and that can be decided, in part, by their debate performance. There's a reason voters should want to know: Nine vice presidents have succeeded to the presidency because of the death or resignation of their political patron.

This is where Palin may have the most difficult task. She hasn't held a news conference since becoming McCain's running mate and has done interviews with ABC, CBS, Fox News Channel, People and Alaskan news outlets.

Her sit-down talks with TV networks did little to shore up her credibility on policy issues. Palin hedged when ABC's Charles Gibson challenged her on the Bush administration's policy of pre-emptive strikes known as "the Bush Doctrine." In the CBS interview, Palin haltingly told Katie Couric that Alaska's proximity to Russia gave her experience in foreign policy — an exchange skewered by comedian Tina Fey in a Saturday Night Live parody.

Palin's performance is under fire even from conservatives such as William Kristol, who wrote in The New York Times Monday that she is in a "defensive crouch" and "has to dispatch quickly any queries about herself" with a strong debate performance. Kathryn Jean Lopez, editor of the conservative National Review Online, wrote Friday that Palin's interviews make her "cringe a little."

"You came off hesitant and unprepared," Lopez wrote. "What happened to the pit bull? I see the lipstick." Calls for Palin to step aside are "not a crazy suggestion," Lopez added.

Other Republicans are trying to set a low bar for Palin. "She's not the master of words that Joe Biden is," former GOP presidential candidate Mitt Romney told NBC.

If a vice presidential candidate flunks the "threshold test" of qualifications for president, voters may well blame the nominee.

Third-party candidate Ross Perot chose former Vietnam POW James Stockdale as his running mate in 1992. Stockdale floundered so much in the vice presidential debate against Democrat Al Gore and Republican Dan Quayle that many voters planning to vote for Perot changed their minds, McKinney says.

2. Can they be aggressive?

Running mates are supposed to be attack dogs, and both Biden and Palin have shown themselves up to the task. But Biden now has to walk through the gender minefield.

If he is too aggressive or combative toward Palin, he risks more than violating the traditional taboo that "boys should not beat up on girls," says Peter Kastor, a Washington University professor who studies American political institutions. He'll also run afoul of the modern prohibition that "in the workplace, men in positions of power can't demean female coworkers," Kastor says.

That came into play in the 1984 debate between Republican George H.W. Bush and Democrat Geraldine Ferraro. In mid-debate, the New York congresswoman objected to the vice president's "patronizing attitude" toward her on foreign policy.

Palin, by contrast, can be aggressive with less risk. "He faces a greater threat of being seen to be speaking inappropriately to her, than she does in some way transgressing what women are supposed to do," Kastor says. On Monday, Palin made a crack about Biden's age and tenure in the Senate, saying that she'd been hearing about his speeches "since second grade" — even though Biden, 65, is seven years older than Palin's running mate McCain, 72. (Biden was first elected to the Senate in 1972, when Palin, 44, was 8.)

The challenge for Biden is to show the benefits of his experience without being boring or pompous, says Sam Popkin, a political scientist at the University of California-San Diego.

"His real test will be can he calmly stick to the issues in a way that lets experience sound like wisdom and not just name dropping," says Popkin, a former aide to President Carter. "It's easier to know a little bit and look good than it is to know a lot."

3. Can they avoid blunders?

Biden's gaffes are frequent and famous. They range from factual slips — he recently said Franklin Roosevelt was president when the stock market crashed in 1929 — to ill-advised ethnic jokes. He said in 2006 that anyone who runs a convenience store "must have a slight Indian accent." But has gaffe-prone become gaffe-proof? Despite his tendency to talk too much and sometimes say the wrong thing, Biden has been re-elected five times.

Jamieson says Biden has made so many verbal goofs that voters no longer get upset about them.

If he has the harder task, Biden also may have more to gain, Popkin says. "This is going to be 90 minutes of Gov. Palin having to deal with a lot of issues. If — a really a big if — if you can make her geniality into superficiality instead of freshness, you can make a difference," he says. "If you make her geniality look superior to your factual nerdy twittiness, she wins."

Palin made a mistake in a 2006 gubernatorial debate, when she advocated teaching creationism in schools, which has been ruled unconstitutional. The next day, she said she did not think creationism should be part of the curriculum, only that it should be able to be discussed if students raised questions.

But in those debates Palin showed the kind of charisma that has been drawing big crowds on the trail with McCain, says her former opponent Andrew Halcro, who ran against her as an independent.

"She did such a great job with just the glittering generalities and filling the room with her presence that people didn't care what she said about agriculture," Halcro says now. "Palin's a master at spending 45 seconds telling you what color the sky is. And people will say, 'That's the greatest thing I ever heard.' "

4. How would they do the job?

The vice presidency is "a very underestimated institution." says Jeremy Lott, author of a book on the position. "All the vice presidents badmouth their own office." His book, The Warm Bucket Brigade: The Story of the American Vice Presidency, takes its title from one of the most famous disparaging remarks about the vice presidency. John Nance Garner, vice president to Franklin Roosevelt, said the job wasn't "worth a warm bucket of spit."

That has changed. Vice President Cheney has been an activist in the No. 2 spot, putting his stamp on energy policy, the Iraq war and the treatment of terrorism suspects. Gore provided then-Arkansas Gov. Bill Clinton with much-needed foreign policy experience from his Senate days, and Gore went on to lead a "reinventing government" push for efficiency.

"People are wanting to know what role they're going to play," says Diana Carlin, a University of Kansas specialist on political debates.

Biden brings foreign policy credentials to the Democratic ticket, while Palin brings executive experience as a governor and small-town mayor to the GOP team. Biden brings longtime Washington experience to a Democratic ticket built on changing the capital; Palin bolsters McCain's conservative credentials with her staunch opposition to abortion without any exceptions and to embryonic stem cell research. "People will be curious as to how they will actually use that background," Carlin says.

The McCain campaign has said Palin would focus on energy policy, drawing on her days as an oil and gas regulator in Alaska. Obama campaign spokesman David Wade says Biden would be "at the table and in the Oval Office for all the big decisions" of an Obama administration. "Barack Obama didn't choose a vice president to farm out an issue here or an issue there. He wanted a full partner to join him in governing."

"People want the vice president to be more than just a funeral-goer, because they have this sense if anything were to happen to the president they want them to be prepared," Carlin says. "But they don't want them to have the upper hand."