Eight years ago, you made The Choice 2000. What was different in the approach you took this time around?

I think the narrative of any good film is based on chronology. We always say to ourselves, "Chronology is our friend," when it comes to making structural decisions about what stories to emphasize and where they should fall in the narrative arc of the film.

In the case of the 2000 Choice, both George W. Bush and Al Gore lived and acted in the same time period -- born in the '40s, grew up in 1950s America, college in the '60s, Vietnam, living as adults in the "me" generation of the '80s and '90s, etc. Their lives could be measured against any number of cultural and political events -- even the music of the times. Chronology was indeed our friend in telling that story.

But Barack Obama and John McCain don't inhabit a common chronology until 2004. Comparing and contrasting the two men along a common timeline was a problem we faced from the very beginning. We choose 2004-2008 as the frame for this film because both of our characters are essentially "running" for the presidency during that time. Both give important speeches at their respective conventions in 2004, both serve in the Senate during this time, both launch their campaigns during this time and both run in the primaries during the spring of 2008. We knew, then, that those events could be the centerpieces of our exploration of the political biographies of the candidates.

Once that timeframe was established, inside those moments we could insert backstory -- political and personal biographical elements that draw on very different time frames: the POW events for McCain happen in the late 1960s; the Harvard Law School events happen to Obama in the late 1980s.

The problem, in terms of the architecture of this film, became one of handling transitions, moving from McCain to Obama and back to McCain again. We spent a great deal of time working on that as well as deciding what backstory elements are inserted into our ongoing chronology. Sometimes our heads were spinning, but I hope, in the end, our viewers are not lost in time or in terms of the progression of the ideas inside the stories.

As a producer, how do you compare the two experiences of gaining access to the candidates and their advisers, friends, colleagues, etc.?

All of the campaigns were very professional. That means none of them made it easy to gain access to the candidate's inner circle or friends or advisers. On this film, the McCain campaign was much more open in the beginning; the Obama campaign was much less open or understanding of our needs. In the end, neither campaign was willing to participate, but by then we had almost everything we needed -- achieved, in the main, by going around them.

In most cases the people who run campaigns aren't geared to understand the difference between FRONTLINE and many other daily broadcast journalism outlets. It's a shame, but, as I say, we prevailed and managed to secure access to more than 60 people with knowledge of John McCain and Barack Obama.

Were there stories you wanted to tell that couldn't make the film because of access issues, time constraints or other reasons?

Of course. Our first cut of the film was three hours long. A great deal of material was left on the cutting room floor. Also, there were some aspects of the candidates' personal lives that were unavailable to us because the campaigns refused to give us access to Cindy McCain and Michelle Obama. I think that is a shame because millions of Americans -- and the people in more than 50 countries around the world -- might have benefited from seeing and hearing from these women, but obviously the campaigns very much want to control the story, and FRONTLINE is harder to manipulate.

We have left out much of the deep biographical background of Obama's youth in Hawaii and Indonesia. We weren't able to find the time to talk as much as we would have liked about the young John McCain as he grew up in a military family.

Politically, we had to leave out the wrangling between the two men over the immigration legislation. We left out McCain-Feingold, and Obama's legislative career in the Illinois State Senate.

In the end, the ideas embodied in those sequences are reflected in other scenes we were able to include in the film, but if there were no limitations of time, I would have included these and a few other scenes in our film.

Delving into the story, were there any discoveries or surprises about the two men?

There were many, and I hope they are evident in the film. In terms of the big picture about the two men, I was surprised at how funny and open John McCain seems to be, and how willing he has been to work in concert with Democrats. Of course he's tough and unpredictable too, but there are those other dimensions to the man that we rarely see.

I always knew Barack Obama could deliver a good speech and that he had what many observers call "political stardust." What surprised me was the level of political skill and calculation that are also deep characteristics of Obama. Many told us he has mastered the art of political infighting, and we saw a variety of examples of that.

In short, John McCain is warmer and more open than I thought, and Barack Obama is cooler and tougher than I thought.

Having conducted so much research and talked to so many people, what do you think is the choice facing voters on Election Day?

The choices facing the voters on Election Day are woven throughout our film -- experience issues and which candidate is most likely to deliver on the apparent desire for change by the American electorate. We've tried our best to shine the light on those moments in the candidates' lives that help viewers answer those questions about the men who are asking for their votes.