Biden and Ryan to face off in US vice-presidential debate The race for the White House is set for another twist tonight with the vice-presidential debate taking centre stage. The single contest between the incumbent Joe Biden and the challenger Paul Ryan has become more important since the gap in the polls has tightened between the main candidates. Barack Obama's campaign has been slightly derailed by his widely regarded poor performance, a fact the president himself has been forced to admit. In another interview he described himself as being "too polite" and sought to play down the impact of Mitt Romney's performance, describing it as good salemanship but running shy of the issues. A week ago, the presidential race appeared to be slipping away from Mitt Romney. But he has managed to erase Obama's once substantial lead in the polls and even edge ahead in some ratings. With the stakes so high, we can certainly expect a more aggressive approach from Obama and the Democrats. More about: American politics, Electoral campaign, Joe Biden, Television, USA presidential elections 2012