Obama hopes battle of the VPs can swing polls

Joe Biden and Paul Ryan will square off tonight in an unusually important vice-presidential match-up that offers the Democrats a chance to regain momentum after President Barack Obama's limp showing in his first debate last week against Mitt Romney.

With polls showing the Republican challenger having wiped out Mr Obama's previous lead, and even taking a small one of his own, their running-mates have been preparing assiduously for their encounter at Centre College, a small liberal arts university in Danville, Kentucky.

Neither is known for mincing his words, and sparks may well fly. In the past few days, Mr Biden – anxious to avoid any trademark off-the-cuff gaffe – has been rehearsing and reading up on Mr Ryan's hard-edged and often controversial economic policies, which is set to be a central theme of the proceedings. "He's going to come at me like a cannonball," Mr Ryan told reporters.

The encounter offers an intriguing contrast in styles, pitting the vastly experienced Mr Biden, 36 years a senator and a former chairman of the Senate judiciary and foreign affairs committees, before becoming Vice-President, against one of the Republicans' brightest rising stars.

Though only 42 (and 27 years Mr Biden's junior), Mr Ryan already chairs the powerful House budget committee and is regarded as the Republican's prime economic thinker on Capitol Hill.

Personally well liked on both sides of the aisle, he is author of a radical plan to reduce the deficit, including part-privatisation of the federal Medicare programme for older Americans, and cuts in government spending in every sector except defence. As such, he – even more than Mr Romney – has been Mr Obama's target on matters economic.

Tonight, Mr Biden will portray his opponent as a blinkered theorist, out of touch with the realities of life for ordinary Americans.

In particular, the Vice-President is likely to zero in on Mr Ryan's Medicare proposals, which are especially unpopular in Florida, a vital battleground state with a high proportion of elderly voters, and seek to expose differences between Mr Ryan and Mr Romney, who in recent weeks has backed away from some of his running-mate's most sweeping proposals, notably on tax cuts for the wealthy.

Foreign policy may be another contentious area. Mr Biden is an expert, who will seek to highlight the Republican duo's lack of experience in the field where a US President has the most freedom to act. Mr Ryan, from the northern state of Wisconsin, likes to joke how "overseas means across Lake Superior to us", while Mr Romney did not exactly cover himself with glory on his summer trip to Europe and Israel.