Biden vs. Ryan: What to Watch For in the Debate Thursday night's showdown in Danville, Kentucky, is generating a lot of interest, thanks to the sense that Mitt Romney's thumping of Barack Obama in last week's debate has seriously hurt the Obama campaign. Cheryl Senter, Madalyn Ruggiero / AP Joe Biden and Paul Ryan Generally speaking, it takes a political junkie to get excited about a vice presidential debate. Sure, showdowns between running mates can be interesting, and occasionally they become truly significant after the fact, if some defining moment - "Senator, you're no Jack Kennedy" - ricochets around the media. But if anyone can find a voter who changes their mind based which of the number-twos argued better, make them an exhibit in the Smithsonian. That said, in Danville, Kentucky tonight, Joe Biden will participate in the second vice presidential debate in a row to draw an unusual amount of interest. Four years ago, ratings for Biden's showdown with Sarah Palin were higher than for any of the presidential debates. The night is perhaps best remembered for Palin's repeated winks at the camera. This time, interest is running higher than normal, thanks to the sense that Mitt Romney's thumping of Barack Obama in last week's debate has blown a hole in the Obama campaign's hull. Suddenly, one debate seems capable of reshaping the race; and suddenly the Obama team needs a shift in momentum. And while Paul Ryan may be no Sarah Palin, he is among the more polarizing running mates in history, sure to draw a surplus of both admirers and haters. PHOTOS: Notes From the Campaign Trail with Paul Ryan So, what to expect? Here are four key themes to watch for: Ryan Plan vs. Obama Record: Count on Biden going hard after the Ryan Plan, the House budget document for which his opponent is famous, and which President Obama once said contains a vision of "social Darwinism." During a recent campaign swing to Florida, Biden warned seniors that the Medicare reform component of the Ryan Plan - which Romney has adopted - would "fundamentally change Medicare. They'd turn it into a voucher program. Biden usually doesn't note that, under the plan, seniors can remain in traditional Medicare if they want. We're likely to hear the same tonight. He'll try to pin down Ryan-more effectively than Obama did Romney-on the elusive details of the Romney-Ryan tax reform plan. And he may repeat past assaults on Ryan for votes he cast in Congress that increased the national debt. For his part, Ryan will parry on Medicare by noting that Obamacare's $716 billion in cuts to the program. And then he will light into the Obama administration's jobs record and the growing national debt. Ryan's campaign events often feature a large digital debt clock ticking away above the stage. He's likely to taunt Biden for recently turning one trillion dollars in new taxes on the wealthy into an applause line. And on foreign policy, Ryan seems primed to make Biden squirm over new revelations about the terrorist attack on the U.S. consulate in Benghazi, and to make the larger argument that U.S. foreign policy is "unraveling" worldwide. Does Experience Matter?: If Ryan goes after Biden on foreign policy, he'll be staging an assault on the vice president's turf. Biden is a true foreign policy expert who, if only by dint of experience, could likely talk circles around his 42-year-old budget-focused foe. Biden will want to show off the depth of his knowledge - and put Ryan on the spot if possible - without seeming to talk down to his opponent. The debate moderator, ABC News national security reporter Martha Raddatz, is also likely to ask tough foreign policy questions. Ryan, on the other hand, might turn Biden's experience against him, noting that Biden has been in Washington 26 years longer than Ryan, and presenting himself as a tribune of "fresh" new ideas. And if Biden leans heavily on the killing of Osama bin Laden, Ryan might remind Biden that he advised Obama against undertaking that mission. MORE: Do Vice-Presidential Debates Matter? Working Class Heroes: Biden and Ryan will compete to be the true champion of blue-collar working America. Biden takes a special pride in his Scranton, Pa., Catholic roots - and he can lyricize about the working man better than almost anyone else in American politics. How many of those hard-working stiffs will be tuned into this debate instead of the baseball playoffs is another matter. Biden is likely to deliver a rousing account of Obama's auto industry bailout, for instance. But Ryan will be fighting for the same piece of turf. On the stump, Ryan has been playing up own small-town Wisconsin roots and his cultural conservatism (though he not to spotlight the fact that he's also a millionaire). Ryan likes to remind voters of Obama's 2008 riff about voters who "cling to guns or religion," then declare "I'm a Catholic deer hunter - guilty as charged." By many accounts, Palin managed to out-populist Biden in 2008. The Gaffe Factor: No discussion of a Joe Biden appearance could be complete without noting that there's no telling what might happen anytime the man will be speaking extemporaneously for an extended period of time. Democrats can take comfort, however, in the memory that Biden's 2008 debate with Palin, as well as his many 2008 Democratic primary debates, were largely Bidenism-free. As for Ryan, he's a far more disciplined speaker, although we've seen recently that he can founder under pressure. And as Dan Quayle learned, you can lose a vice presidential debate simply by being on the receiving end of a great zinger. Biden's got some of those, too. Which could make things entertaining-for whoever is actually watching the under card perform. MORE: Let There Be Joe Biden