DANVILLE, Ky. (AP) — Democrat Joe Biden and Republican Paul Ryan were under pressure Thursday to help boost their tickets out of a closely fought battle for the White House as the nation's eyes turned to the pair of scrappy vice presidential nominees meeting for their only debate.

The showdown matches up two skilled politicians with strong policy credentials and very different styles. It's 69-year-old Biden's folksy appeal and solid vice presidential portfolio vs. 42-year-old Ryan's intensity and extensive knowledge of the federal budget and economy from 14 years in Congress.

Warming up President Barack Obama's crowd at the University of Miami's basketball arena, Florida Sen. Bill Nelson predicted: "Tonight, Joe Biden will make mincemeat of Paul Ryan." Obama, himself, didn't mention Biden while encouraging the crowd to take advantage of early voting in Florida, but he did call Biden from Air Force One en route to the rally to wish him luck.

Ryan signaled he's ready for whatever Biden sends his way.

"I'm not intimidated, I'm actually excited about it," he said on CNN.

With the spotlight on the running mates, Republican presidential nominee Mitt Romney spent the morning in secluded practice for his next face-off with Obama on Tuesday. He then flew to North Carolina, where he visited the Rev. Billy Graham before an evening rally in Asheville with country singer Ronnie Milsap.

The vice presidential debate will help to shape the campaign narrative until Romney and Obama meet again Tuesday for the second of three debates. Obama is eager to change the vibe after his lackluster performance in the first debate and Romney's recent gains in the polls. Romney, for his part, is hoping a strong Ryan performance will help propel Republicans forward on an energetic drive through the campaign's final weeks.

"Looking forward to it," Biden said Thursday as he boarded his plane for Kentucky with his children and Rep. Chris Van Hollen, D-Md., who played Ryan in practice debate sessions. The vice president then holed up with his traveling entourage in a private home near the debate sight. His GOP challenger stayed out of the public eye all day Thursday. Aides reported that he spent time with his family, studied debate briefing books and exercised.

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Democratic Kentucky Gov. Steve Beshear encouraged Biden to turn in a tougher performance than Obama. Beshear said Obama "didn't do well" in the presidential debate and should have mentioned Romney's dismissive comments about the 47 percent of Americans who don't pay income taxes.

"My guess is that he was advised to be presidential and don't get into the fray and look like you are above the fray and all that," Beshear said in an interview with The Associated Press. "But there is a difference in doing that and being aggressive and making your points and pointing out the difference between your two candidates."

Obama's campaign posted a photo on Twitter of Biden and Van Hollen practicing for the debate. They sat side by side in suit jackets and no ties on a set designed to look like the debate stage at Centre College, a liberal arts school with just 1,340 students.

The brief glimpse into Biden's debate preparations, with the vice president sitting with a coffee cup in front of him, is a marked contrast from the total secrecy that surrounded the president's practice sessions. Obama's aides have refused to even discuss the most basic details of his debate preparation.

Biden kept the mood light during practice runs this week in his hometown of Wilmington, Del., aides said. He bought his team subs for lunch Monday from a local sandwich shop and kept a supply of animal crackers and M&Ms on hand. The team spent most mornings in policy discussions at a hotel near Biden's home, with mock debates in the afternoon.

Aides joked that the sparring partners spent so much time together this week that they were even starting to dress alike. Both men showed up to debate practice Wednesday in blazers and blue dress shirts.

The 90-minute debate is sure to draw a television audience of tens of millions. But it's unlikely to eclipse the 70 million who tuned in to watch Biden face off with Republican firebrand Sarah Palin four years ago.

That debate was more of a curiosity: It allowed Palin to outdo Biden in folksiness and recover from a series of painfully awkward media interviews but did little to alter the trajectory of the race.

"Joe just needs to be Joe," Obama said, when asked his advice for the vice president in an interview Wednesday with ABC News.

Thursday was a rare day when the political activities of the running mates were taking center stage and those of Obama and Romney were seen as secondary. But with just 26 days left until the election and the race still tight, neither Obama nor Romney was completely ceding the spotlight, with each holding a rally in a swing state.

Obama told the Florida rally that Romney is changing his positions after winning the Republican nomination to appeal to general election voters. "After running for more than a year in which he called himself severely conservative, Mitt Romney is trying to convince you that he was severely kidding," the president said to laughter from his supporters.

Obama also was attending a fundraiser in Miami featuring actress Eva Longoria and singer Sheila E. About 700 people were expected, with tickets costing between $500 and $10,000 per person. Obama campaign spokeswoman Jen Psaki said the fundraiser would be one of the final ones of the campaign for the president.

Thursday's debate, moderated by Martha Raddatz of ABC News, will cover both foreign and domestic topics. The debate is to be divided into 10 segments. At the outset of each segment, Raddatz will ask an opening question, and each candidate will have two minutes to respond.

Both Biden and Ryan head into the debate with vulnerabilities: Biden must rein in a freewheeling manner that can be endearing but also produces plenty of gaffes. Ryan hasn't been in a campaign debate for more than a decade and is light on foreign policy experience, a sharp contrast to the vice president, a former chairman of the Senate Foreign Relations Committee.

Ryan also will need to find a way to reinforce Romney's policy positions without selling out his own, more conservative credentials.

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Associated Press writers Julie Pace and Nancy Benac in Washington, Ken Thomas in Coral Gables, Fla., and Robert Ray in Wilmington, Del., contributed to this report.