Barack Obama and his Republican foe Mitt Romney will clash on Wednesday in Denver, Colorado, in the first of a trio of debates, a test of nerve, temperament and presidential mettle before tens of millions of viewers.

The televised debates, which have the feel of a heavyweight title fight as a feisty challenger seeks to knock out or outpoint the current champion, are the last best hope for Romney to save a sagging campaign.

And they represent a potential minefield for President Obama as he seeks to cling on to a narrow lead in his quest to win a second term on Nov 6.