The question was, would the American people elect him? Hillary Clinton had helped heal Democratic divisions after a bitter primary fight. But Obama entered the convention locked in a dead heat with Republican opponent John McCain.
Obama's acceptance speech attracted 84,000 people to Invesco Field in Denver and another 40 million to their television sets all across America - more people than watched the opening ceremony of the Olympics.
60 Minutes and correspondent Steve Kroft was waiting backstage just moments after the most improbable nominee, joined by his vice presidential choice Joe Biden, had given the biggest speech of his career.
Asked if he ever doubted the nomination was going to happen, Obama said, "Of course."
"When?" Kroft asked.
"Well, let's see. About a year ago we were down 30 in Iowa," Obama said, laughing. "Ya know, but I never doubted that it could happen. I never doubted that, if we were able to mobilize the energy that you saw in that stadium."
"All across the country," he added.
"I knew it was gonna happen before he did, I was running like the devil. I watched. I thought I was pretty good, but I watched. I watched, this guy just sort of grabbed the lightening, ya know, just grabbed it. And you could tell, Barack, I tell ya, my team knew, I knew in August," Biden recalled.
By the time Kroft and Obama continued the conversation the next day in Pittsburgh, the political landscape had already changed. Senator McCain had tried to steal the Democrat's thunder by announcing that Alaska Governor Sarah Palin would be his running mate
Asked what he thought of Palin, Obama told Kroft, "She seems to have a compelling life story. Obviously, she's a fine mother and an up-and-coming public servant. My sense is that she subscribes to John McCain's agenda."
"Does the fact that he chose as his vice president someone what has less experience than you take that weapon out of his arsenal?" Kroft asked.
"Well, you know, I think that's a good question to address to Senator McCain," Obama replied.