After the poor debate performance of U.S. President Obama, his vice president is burdened with great pressure to make up for it, and challenger Paul Ryan is of a higher caliber than 2008’s challenger, Sarah Palin. Joe Biden had better not repeat this sentence: “The middle class was buried the last four years,” the vice president let slip last week in the election campaign. It was not a good choice of words for a politician who is contending for a second term of office — even if Biden wanted to say that the deadlock in Congress has harmed the citizens. The vice president is known for his down-to-earth demeanor and his political instinct, but also for gaffes and verbal blunders.

The U.S. Democrats are holding their breath. If there is anything they don’t need at the debate of the vice-presidential candidates this Thursday, it is a “Biden gaffe.” Actually the debate between Biden and Paul Ryan, vice presidential candidate of Republican challenger Mitt Romney, should have been a second-string game. But after Obama’s weak appearance in the first duel with Romney, Biden is burdened with high expectations: The deputy must bail out his boss. In the past few days, Obama has sustained the loss of his edge in the polls that he had built up after the party convention. In some polls he is now even behind Romney.

Most observers believe that Biden has a good chance of passing the test. The offhand slip-ups most often happen to the affable vice president when he mingles with the people. In debates, the former senator has demonstrated discipline and expertise. A further strength of the 69-year-old: He is considered down-to-earth and likeable — unlike his boss, who seems aloof from time to time. At the party convention in Charlotte, Biden heated up the mood among the delegates with a catchy speech.

Biden’s strong presence may well help him in the confrontation with Ryan. Nevertheless, he is up against a different caliber of opponent than in 2008. In 2008 he competed against John McCain’s vice presidential candidate, Sarah Palin. The former governor of Alaska had already damaged herself with an apparent lack of knowledge of the facts before the debate. Biden’s most important task was not to seem pretentious.

Congressional representative Paul Ryan is a greater challenge. The ambitious 42-year-old is one of the most influential economic politicians of his party. The House of Representatives budget expert is the author of a well-known plan to cut the deficit. Ryan can juggle numbers until his partner in conversation is dizzy: In a six-minute monologue at a summit to which Obama had invited the opposition in February 2010, he made mincemeat of the plans for health care reform that the Democrats pushed through Congress in March 2010. “This bill does not control costs,” was Ryan’s hard bottom line.

For Biden, it will be a matter of riding out Ryan’s storm of numbers and using the political battleground that his budget plan presents. He could pounce on the budget’s suggestions for Medicare reform — a hot topic in important states like Florida, where many retirees live. If Biden can convince viewers that the Medicare reform that Romney and Ryan are proposing would harm America’s senior citizens, he could win points.

Biden can also try to shed light on political differences between Ryan and his boss. So Ryan, who hails from the state of Wisconsin in the Midwest, voted for the government bailout of automaker General Motors — Romney was against it. “Osama bin Laden is dead and General Motors is alive” is one of Biden’s favorite slogans in the election campaign, which sheds light on one of Obama’s greatest successes: the killing of America’s public enemy number one.

It is too bad for Biden that foreign policy plays such a minor role in this election campaign; though Ryan is inexperienced on the topic, the former chairman of the Senate Committee on Foreign Relations looks back on several decades of experience. When Biden was elected to the Senate for the first time in 1972, Ryan was two years old. The vice president was closely tied to Obama’s most important security decisions — from the end of the war in Iraq to the drone war against terrorists in Pakistan. During a campaign stop in Ohio on Monday, Ryan echoed Romney’s criticism of Obama’s foreign policy and charged the president with weak leadership in the current crises in Syria, Libya and Iran. How Ryan does with foreign policy in the debate will lay the ground for next week, when Romney and Obama discuss the very same topic in their second debate in New York.