John McCain by Pool Photographer/WireImage.com; Barack Obama by Sven Darmer/DAVIDS/WireImage.com
The ratings record set when Ronald Reagan debated President Jimmy Carter in 1980 - 81 million viewers - could be broken on September 26 when Sen. Barack Obama and Sen. John McCain meet in the first of three match-ups that may decide who prevails in his quest for the White House. "The stakes are never higher than in a debate," says CBS News analyst Dan Bartlett, former counselor for President Bush. "The overall tension and anxiety is incredible." Here's what to expect:

Put in classic TV terms "McCain has to be Matlock," says political analyst and former Democratic consultant Dan Payne. "The old defense lawyer who is folksy but smart. He can't be Wilford Brimley, the cranky old man. Obama has to be Cliff Huxtable - a likable dad with a strong sense of right and wrong." MSNBC's Pat Buchanan adds that Obama "cannot let McCain beat him up without showing some movie and fight. If he can win this debate, he is a favorite to win the election.""

What do the candidates need to avoid? "McCain can't have a senior moment," says Payne. "One or two mistakes and you'll see a drop in the polls." As for Obama, he has to appear knowledgeable without getting long-winded. "If you ask him what time it is, he tells you how to make a watch," Payne says. "He has to make his answers and responses crisper and more to the point," Bartlett agrees.

You'll hear President Bush's name a lot - just not from McCain, and not in a good way. "I'd advise Obama to say the words 'George' and 'Bush' as frequently as possible," says Fox News contributor Howard Wolfson, the former communications director for Sen. Hillary Clinton's presidential bid. "His campaign has rightfully hit on the strategy that John McCain represents four more years of George Bush." But Bartlett warns that Obama should be careful about overdoing it. "McCain has a lot of high profile issues where he didn't agree with the president," he says.

A gaffe or misstep can be fatal in today's video-saturated environment. Any goof will get replayed and even remixed on YouTube. The candidates also have to be careful about producing fodder for pundits and late night comics. Even body language and mannerisms matter, says Bartlett, who recalled how Al Gore's audible sighs were lampooned on Saturday Night Live. "It's important how the candidates handle an unpredictable moment," he says.

The vice presidential debate will matter more than ever because of curiosity about McCain's running mate Alaska Governor Sarah Palin, who squares off against Sen. Joe Biden on October 2. "It will be used as a bellwether on McCain's judgment," Bartlett says. Buchanan says "Biden has a problem: how to show Sarah Palin is an untutored lightweight without being condescending. As for Palin, she has a fine wit, which won for Reagan, and will be prepped to use it." But past veep showdowns have never been in a decisive factor in a campaign. Remember how Lloyd Bentsen stunned Dan Quayle by telling him he was "no Jack Kennedy" in 1988? George H.W. Bush still won the presidency in a landslide. "In the end," says Wolfson, "these elections are decided by the top of the ticket."