>>> 7:43. what were you doing in your 20s? maybe you shouldn't answer that, but this man spent his at the hand of the president writing history. he will end his tenure at the ripe old age of 31. willie spent time with him.
>> good morning. john started writing campaign speeches for john kerry at the age of 22, a few months removed from his college graduation. he later teamed up with a freshman senator named barack obama , that now calls him his mind reader. the departing speechwriter takes us inside his life as the voice of the president.
>> with common effort and common purpose , with passion and dedication, let us answer the cal of history.
>> this is the second nauinaugural right here? one of the drafts the president wrote up.
>> his very neat writing.
>> reporter: john has spent the last years taking notes like these and turning them into soaring speeches for barack obama .
>> generation of americans have responded with a simple creed that sums up the spirit of the people, yes, we can. yes, we can.
>> reporter: the two have been unacceptable writing partners since he joined then senator obama in 2005 . four years later, at 27 years old, the massachusetts native became the second youngest head speechwriter in the history of the white house .
>> there's a lot of focus on your age. people are obsessed you're this wonder kid. did you ever stop and say, i might be in a little over my head here?
>> all the time i think i'm in over my head .
>> of course. especially when you're writing for the president.
>> reporter: he hit the ground running, writing for the inaugural address . making the case for health care reform .
>> i'm not the first president to take up this cause but i am determined to be the last.
>> scrambling to finish a nobel prize acceptance speech aboard air force one.
>> for a variety of reasons it would be a difficult speech not the least that the president said i'm not sure i deserve this.
>> he spent the night before going to lows writing material . during the flight, everyone falls asleep and we are trying furiously to write the speech. it was one of the only moments we didn't know we would have a speech ready by the time he gave it. he handed us literally as he was going to the elevator to the stage and we put the final words on the prompter right as he was walking up.
>> at this moment of challenge, this must be our work.
>> how close were you not getting that speech in the prompter?
>> uncomfortablebly close.
>> with his age, looks and proximity to power, he became a star quickly. one of "time" magazine's most influential people and most beautiful. and asking about his relationships after he was spotted with actress rashita jones.
>> what do you think of this celebrity?
>> i've always been told never take your job or yourself seriously. this is more fodder for my friends that mock me relentlessly for than anything i take seriously.
>> favreau's job is most difficult during times of a national crisis.
>> word of a school shooting at an elementary school .
>> you're not a parent yet but when you're a parent, having a child is like walking around all day with your heart outside your body.
>> suddenly exposed to the world. to possible mishaps or malice.
>> that was a line we ended up using in newtown. in the eight years i've known him, i've never seen him like that. it affected him very deeply.
>> reporter: even as favreau wal walkses way from the white house he expects he hasn't heard the last from his friend at the white house . i said i might be there if he needs me and he said once in a while i might cal and i will pick up the phone .
>> you will not send him to voice mail ?
>> no. that's a call i will pick.
>> he plans to open a consulting office in washington with a friend also leaving tomorrow. ultimately he has his eye on- screen writing for television. as for the president's next speechwriter, the white house has decided to go with somebody a little older this time. cody keenan is 32.
>> there's something about youth at the white house that works, has favreau seen television lately? does he know what he's getting himself into?
>> he is going to try and a friend, john lovitt , a former speechwriter in l.a. and says, come give it a try out here.