A very interesting point was made by a stand-up comic, John Fugelsang, last night. Denver is one of the USA's highest cities above sea level. When Fugelsang played a gig there for the first time, he found it difficult to think and breathe.
Romney was there for a few days before the debate and could acclimatise while Obama flew in with a few hours to go. Having watched the debate in full and seen a simply woeful performance from Obama, I can well believe that the schoolboy error of not taking the 'Mile High' city seriously might well have cost Obama the debate last night.