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Four years ago, Joe Biden was careful not to appear overly aggressive in his vice presidential debate with Sarah Palin, then a newcomer to the national stage.
Now, as he prepares to debate Paul Ryan, a 14-year House veteran and the top Republican budget writer, Biden is less concerned about looking like a bully.
"I think he is going to play hardball," said former Michigan Gov. Jennifer Granholm, who played Palin in debate preparations in 2008 but is not involved this year. "He won't have to worry about pulling punches. He can go after policy and raise issues with a number of deliberate deceptions the other side has put forth."
Vice presidential debates typically don't matter as much as presidential face-offs, but both parties say the stakes for Thursday's clash in Kentucky are higher because of President Barack Obama's lackluster showing in last week's presidential debate.
A strong performance lifted Republican Mitt Romney, helping him cut into Obama's lead in key battleground states. Officials in both parties anticipate that Vice President Biden will be notably more aggressive than Obama, repeatedly taking the fight to Ryan as Democrats try to regain their footing in the closely fought election.
"Obviously, what we expect is the vice president's going to come at me like a cannonball," Ryan said this week.
The 42-year-old congressman must overcome a lack of foreign policy expertise and experience in national debates, although Democrats praise his encyclopedic grasp of budget details and ability to think on his feet.
"Paul Ryan is an inside Washington guy, smart and wonky. He knows the budget better than anybody," said Granholm.
Biden is likely to press Ryan to defend Romney's proposals on taxes, Medicare and spending — and seize any opportunity to tie Romney to a House Republican budget written by Ryan. Democrats say the GOP budget contains severe spending cuts unacceptable to most voters.
Rep. Chris Van Hollen of Maryland, the senior Democrat on the House Budget Committee, where Ryan is chairman, said his colleague "has a fundamental choice to make" in the debate.
"He can either come clean about the negative consequences of the Romney-Ryan budget and tax plan, or he can continue to hide the ball like Mitt Romney did the other night," said Van Hollen, who is playing Ryan in debate preparations.
An effective performance by Biden, a former senator who essentially made a career out of debating colleagues, could help quell nervousness among some Democrats, although neither party expects undecided voters to be swayed by the vice presidential duel.
A skilled retail politician, Biden is known for going off script. Last week, he said the middle class had been "buried" during the last four years, a remark Republicans turned into an attack on Obama.
Democrats say Biden brings an authenticity that voters relish.
"If you want someone who gets middle-class America and gets family in America, Joe Biden is absolutely the best person you can find," said Sen. Chris Coons, D-Del., who holds the Senate seat Biden held for more than three decades.
Biden, 69, has participated in numerous debates, both as a presidential and vice presidential candidate, and has tended to be more disciplined in those matchups than on the stump. A foreign policy expert, Biden also is helped by his close relationship with Obama. Biden often is one of the last people Obama consults on major decisions.
Republicans have spent the last few days raising expectations about Biden. Republican Party Chairman Reince Priebus, who regularly ridicules Biden as a gaffe-prone campaigner, changed his tune over the weekend, telling CNN the vice president will be a formidable opponent for Ryan.
"I think people realize that Joe Biden is a gifted orator. He is very good at rhetoric, and I think he is very relatable so I think it's two different people, and I think it's going to be a great night," Priebus said.
Biden said he is looking forward to the debate.
"All debates are tough," he told reporters in Iowa, the day after the Oct. 3 presidential debate in Denver. "You can sit there and say I would have done that, I would have done this. Well, nothing like standing up before 30, 40, 50, 60, 70 million people."
Biden said he has been "studying up" on Ryan's positions to prepare. "I just want to make sure that when I say these things that I don't have the congressman say 'No, no, no, I don't have that position,' " Biden said.
"We have a fundamentally different view on a whole range of issues," he said.
Biden has been closeted in his hometown of Wilmington, Del., since Saturday for practice sessions with Van Hollen and prep work with his staff and top advisers to Obama, including senior campaign strategist David Axelrod. Biden has participated in mock debates and studied videos of Ryan's speeches and interviews.
Ted Kaufman, a longtime staffer who replaced Biden in the Senate after he became vice president, said Biden is comfortable in debates, but faces a crafty opponent in Ryan.
"The problem with this one is you just don't know what Congressman Ryan is going to say," Kaufman said, noting what he called Romney's repeated disavowals of his own proposals on taxes and others issues during last week's debate. Democrats expect the same from Ryan, Kaufman said.
At his acceptance speech at the Republican National Convention, "Ryan said a bunch of stuff that wasn't true," Kaufman said, citing Ryan's claim that Obama had failed to deliver on a promise to save an auto plant in Ryan's hometown of Janesville, Wis. The plant closed before Obama took office.
Ryan also faulted Obama for a proposed $716 billion Medicare cut that Ryan embraced in his own budget.
Despite those concerns, Kaufman said his advice to Biden is to focus less on his opponent than on his own performance. "I think the best thing you can do in one of these things is to be yourself," he said.