The debate at Case Western Reserve University in Cleveland on Tuesday will reveal two vastly different characters in the running mates of Republican President George W. Bush and his Democratic rival for the White House, John Kerry.

Cheney, one of the hawks of the US administration, has often been accused of operating in the dark shadows of American politics. Experts say he is one of the most influential vice presidents of all time.

And he has taken on the role of attack dog in the Republican campaign for the November 2 election.

The youthful Edwards has taken a secondary role in the battle for the White House.

The 63-year-old vice president has proved a past-master of the negative attack while Edwards, 51, is a successful trial lawyer who made a point of avoiding negative attacks during the campaign for the Democratic nomination.

Cheney uses dry humour a lot to make political points in his speeches.