President Barack Obama and Mitt Romney at last stand face-to-face on Wednesday to duel for the White House in the first of a trio of debates just 33 days before American voters decide their fates.
Obama heads into the showdown in Denver with a narrow lead in his bid to defy historic omens sown by a stubbornly sluggish economic recovery, and to become only the second Democrat since the second world war to win a second term.
Republican Romney, down in almost all the key battleground states that will decide who wins the 270 electoral votes needed to win on November 6, seeks a sharp change of momentum in a race that seems to be slipping away.
The rivals will step up to podiums at the University of Denver in the Rocky Mountain state of Colorado, at 7pm (local time) to clash over the economy and other domestic issues.
But veteran anchor Jim Lehrer, who will steer the debate for tens of millions of viewers at home, has leeway under rules thrashed out by the two campaigns to bring up other burning issues.